My choices:
# 2010/03/26 - Watarirouka Hashiritai - 1st Swimsuit PB [Akkanbe~]
Just the fact that we can talk about Mal owning this book and the Lovetan poster he got makes this one of the best group PBs
# 2010/04/30 - AKB48 - AKBINGO! Official Book
Cheap and really nice to have. Good overview of the show, new pics, nice variety
# 2010/07/22 - AKB48 - VISUAL BOOK 2010 featuring Team B
B! B! B! Wasshoi!
# 2010/09/17 - SKE48 - Gakuin Shuugaku Ryokou (Kyoto/Nara trip)
Great fun, pretty stuff.
# 2010/10/15 - Team KISHIN - [Mado kara Sky Tree ga Mieru]
For art value.