What is "The Black Rock Ledger" good for?

I recently got a page of "The Black Rock Ledger". It cannot be sold and except reading its text it does not seem to have any other purpose (except wasting stash/inventory space).

Should I keep this item? Will it be usable for something later? Maybe the all-mighty Cow Level?

It's an easter egg, referencing the TV series Lost. The page numbers 4, 8, 15, 16, 23, and 42 are also part of the Lost reference. Basically, you can throw it away if you want to, or keep it in your private collection.

Don't throw it away. There might be something to it. Some have speculated there is more Lost Easter Eggs linked to it, concerning the black tornadoes that randomly pop up in the deserts. The reason is the Smoke Monster in Lost and the fact that the tornadoes look be made of smoke. I don't know, try going into one of those tornadoes with all Ledgers in your inventory, or perhaps throwing them all into the tornado. Who knows, anything is possible when it comes to Blizzard's sense of humor.