If i could help you i'd put the address of a site i know in
italics like this, or tags, but i think the moderator would frown on any website mentioned. *ahem*. Anyhow, there are only a few differences between the manga and anime upto about 20, but there is some argument over the difference of Galatea's arrival in the slashers, but that's about it. I must admit i've never seen claymore in a bookstore, but i live in a marsh, so it's hardly metropolitan, i was introduced to it by my housemates at university after we were all drunk and pumped up from watching metalocalypse on adult swim. I'd advise reading right from the start to get a good feel if you've got the time, you won't get too derailed by the differences then. The Teresa arc is many peoples favourite, but all the action and plot begins around the slashers, after that it's the war in the north that became the let down in the anime. The manga is still ongoing, and this month had no scene
so lots of people are getting withdrawal but the story continues to about 78, and the invasion of pieta was around 55ish so it's not too long.
Good luck on your search, happy to help however i can, send me a message if you really, still need help...