Fastest way to get enchanted books?

I do not know if there is any set documentation on the various times/efficiency for getting enchanted books, but let's take a look from gameplay experience.

1. Fishing

This is not likely to be the fastest way, as fishing is meant for, well, fish. According to this, a vanilla Fishing Rod only has a 5% chance of catching a treasure, and from that 5% chance, there is only a 0.8% chance that it will be an Enchanted Book. So, your odds aren't so great.

2. Dungeon Looting

Dungeon chests have a 15.1% chance of spawning an Enchanted Book. As the frequency of dungeons is already limited, again, this method is not so great.

3. Enchanting

This could be the best way, although other auto-fishing methods could work. By setting up a mob farm to generate XP, you can easily enchant multiple books at the highest possible level to do so. There are various YouTube videos and guides on setting up efficient mob farms, so that may be beneficial to check out.

The absolute fastest way to get a lot of enchanted books is to set up an AFK Fish Farm and leave it running overnight.

As I found out, chests in the librarys of Strongholds will mostly provide Enchanted Books. However, you'll need Eyes of Ender to locate one. You'll need Blaze Powder (crafted from a blaze rod from Blazes in the Nether), and Ender Pearls (from killing Endermen). Another way is to go fishing. Enchant your fishing rod for most likely a change for some loot.

You can also enchant books too. Just craft a book using 3 pieces of paper and a piece of leather, then go to a nearby enchanting table and put the book in the slot (lapis is now required for enchanting items). Chose an enchantment, now that you won't have to take a guess and which enchantment to use now that you can hover over an enchantment and it'll say the effect.

If you are in version 1.14 or higher, find a village or cure a zombie villager. Use a lectern to make it a librarian and trap it. Then check the trades. It should have an enchanted book. Break the lectern, wait for the villager to become unemployed, and place it until you get the right books and trade. Be careful; it won't work once the villager levels up.

See 2021-05-20 edit at end.

As of 1.16 on Bedrock, AFK fishing is the fastest, cheapest and safest way to get enchanting books early and mid-game. And you have a chance to get 'Mending' enchantment. Latter on when you develop your world, a trading post with villagers may be better suited for you if you like big projects.

It does the best with an 'autoclicker' app of some sort so its not the 'purest' form of Minecraft. Otherwise you need to click the 'fish' button yourself. But with an automatic fish farm setup you do not need to click 'fish' to reel in your catch, it does it automatically. You can fish while watching a movie!!

My thoughts and suggestions on the matter:

At the very start of your fish farm (or fishing in general), the treasure drops are very low with a plain fishing rod. But before long you will catch some junk rods that have 'Lure', 'Luck of the Sea' or 'Mending' (or combinations of). It's as simple as combining one with a fresh rod or a rod with 'Mending' and it will snow-ball after that. After an hour of fishing with a fully enchanted fishing rod I usually get a lot of enchanted bows and rods, as well as about 3–5 enchanted books.

It's safe because you can enclose your fishing spot. Only the block above the bobber needs to be open to the sky. But make sure that it is a chimney style opening so that creepers do not wander in and spoil the fun (learned that the hard way).

Don't forget that you get XP from fishing as well as lots of raw fish. If you have an automatic smoker attached, you will get lots of food (cooked salmon fills 3 food icons) and even more XP. You may waste more fuel with a smoker because you can't fish fast enough to keep up. Either put on a switch to allow smoking fish in batches or use an oven.

I am talking about a fish farm setup that has a water logged chest against a body of water and below that a lava/hopper cart collection system (Google 'minecraft 1.16 bedrock afk fish farm'). My previous world my base was in a 'plains' biome so I needed to make a 5x5x5 fish tank. My current world I constructed it beside an ocean--with a nice big glass wall facing west so that I can see a beautiful sunset;).

...And I haven't even made an enchanting table yet!!! And all my equip/armour are fully buffed (a few times over because I died several times where I couldn't reclaim my stuff--poo!).

Somehow my 5x5x5 fish tank yielded a much faster enchanted book rate than the open ocean farm. I don't know why yet but in the fish tank I added several tropical fish types that I got from traders. I suspect that the fish are always in proximity in the fish tank whereas in the open ocean the local density of fish fluctuate all the time. However, in the fish farm tutorials/wiki, there is no mention of fish density affecting the rates. I am thinking of enclosing a 5x5x5 or larger space with glass at my ocean fish farm and keeping some fish in the space. I'll let you know if the rates improves.

Edit: It does increase the catch speed. I added a 5x5x5 glass enclosure around my fishing area and put in some puffer fish I got from the wandering trader. I believe that having the fish in close proximity decreased the wait times. I was casting 8 sec. per cast before and felt that I would miss some catches. Now I have it down to 6 sec. per cast and feel like I wasn't missing many catches. 5sec. per cast was too low. Now only after 1hr of AFK I was getting around 8–10 books.

2021-05-20 Edit: Still works in 1.17 Beta. Current click duration is 6sec/cast.

I really want to help people out on this topic but I don't have enough reputation (yet;) to make comments. And it doesn't produce 1 per hour as RudolfJelin describes below (there must be something wrong with that farm or its a troll). You will get over 5 books an hour. I think the best setup is not to make your AFK fish farm in an open ocean or lake, but make an enclosed tank with fish. I made mine an enclosed tank with glass in an ocean only so it looks pretty for me. Try to search YouTube for "1.16 AUTOMATIC FISH FARM" and look for JC Playz' video. He does it in creative mode but its not hard to make while in creative with very cheap materials. I use up-turned trap doors to prevent me from stepping into the hole but you can experiment yourselves.

By the time I started to hunt for blaze, arguably 'early to mid-game', I had about 3 double chests of extra enchanting books and all my equipment maxed out. The hardest part was to get enough XP to combine books and equipment on the anvil. I was still only developing my XP kelp farm at the time. And I threw out any books that had curses and any that only enchanted bows and fishing rods (bows and rods come already enchanted as loot). By the time I faced the Wither, I had sorted out enough books to enchant my equipment 5 times over and still have over 4 double chests of unsorted books. I know because I died many times with that wither;) Now I am pretty sick and tired of sorting out enchanting books. :P

So by at least mid-game you will have enough enchanting books, with Mending, to last you the rest the game. Only Soul Speed is not available by fishing.

I admit I am not a 'large project' type of player so villager farms are to big for me to undertake. We are all different in play style, so I can only speak to those that need simple early game solutions.

If you are willing to make a village farm, then the only advantage for fish farm is that many books will come with multiple combinable enchantments that may reduce the number of 'anvil uses' that the specific equipment receives. But at late game, anvil uses becomes irrelevant. (I don't mean anvil durability but increasing XP costs per anvil use for a piece of equipment--what's the right term?)