9/2011 is they'll be coming out with the new books for all levels. The new books will have several new patches for each level (Daisy, Brownie, Jr, Cadett, etc), they will do away with several of the excisting patches & they're combining the Handbook & the Patch book for each level.
At this time I would not suggest you buy the present Interest Patch book until the new one comes out.
In the meantime if you're daughter is planning to earn her Silver award, then I recommend she complete a Journey book appropiate for her age. The Journey book does not have to relate to her Silver Award Project.
If she wants to do an Interest Patch, you can always go to your Council Office Resource Room & make a copy of an Interest Patch your daughter is interested in doing but make sure to buy the patch at the same time. Or ask a leader to borrow her book to copy the IP's she's interested in doing until the new books come out. Remember as they're eliminating some of the patches from the patch books, they will also discontinue selling those patches in the store.