I have been looking for books or articles that help with isopod identification.
What type of isopods are you looking for? Terrestrial, freshwater, marine? Any specific geographic area in mind?
A quick Google search (isopod identification) turned up this:
Try https://bugguide.net/node/view/14/bgref The Wayback Machine should help with some of the broken links.
One from the bugguide list:
Mainly Terrestrial Isopods but I am interested in the whole order and no particular area.
Thank you this is helpful.
I recommend the BugGuide list too. In North America, especially the northern half of the continent, there’s very few terrestrial isopod species. Most of them are introduced and easily IDable. I learned most of my local (South Ontario) isopods by just comparing them to other iNat obs and BugGuide photos. It only gets challenging with odd individuals or uncommon species
For British: Invertebrate types: woodlice by S. Sutton. But out of print and rather expensive.
I forgot there is a more up-to-date id guide for Britain, by S. Hopkin, and still available.