Combining multiple find commands into one

I have a bash file with the following commands to copy books from my books folder into my toread / Read Later folder

find /books -name '*.pdf'  -exec cp -n {} /toread \;
find /books -name '*.epub'  -exec cp -n {} /toread \;
find /books -name '*.azw*'  -exec cp -n {} /toread \;
find /books -name '*.mobi'  -exec cp -n {} /toread \;

I want to get rid of the repetitiveness of these commands and batch the actions into one?

-o in find expression is logical "or". There's a quirk though: juxtaposition (which is an implied "and" operator) takes precedence over the -o operator. For this reason you often need parentheses. They should be escaped or quoted, otherwise they will be interpreted by the shell:

find /books \( -name '*.pdf' -o -name '*.epub' -o -name '*.azw*' -o -name '*.mobi' ')' -exec cp -n {} /toread \;

Note I deliberately escaped the opening parenthesis and quoted the closing one, just to show the two ways.

Without parentheses the -exec part would apply only to *.mobi files (compare this question).