I've noticed some achievements seem to only trigger a check to see if you've earned it on certain pages - usually collection pages or the shops where things that go in collections are bought. I haven't figured out how to trigger a check for the bookworm achievement, however. judging by the intelligence stat on my main pet, i think i should qualify for two levels of bookworm. is there a collection page for books a pet had been read? is that how to trigger the check? or am i just being unlucky with server calls and my observations were weird random luck?

Yeah, AFAIR you need to go to your pet's 'Books Read' page - go to Pets > the dropdown at the top right of your pet (just above their stats) > Books Read. Food achievements trigger the same way.

For specific book achievements, go to the achievements page and click Show Required Items for each achievement.

ah, i honestly probably would not have found that particular part of the menu on my own for quite a while - thank you so much!