I currently only own two hamster books, the Hamsterlopaedia and the RSPCA Care for Your Hamster.
Both these books have pros and cons, but the one that is by far my favourite is the Hamsterlopaedia. It is so packed full of hamstery information that I can't really fault it. The stuff in there is priceless, especially the health section. If I'm ever in doubt I turn to that, and it usually answers any questions I have.
The RSPCA one I am less enthusiastic about. It is good to a certain extent but some of the information is sightly outdated. The pictures are beautiful though, and it does have little titbits of useful info.
I bought this one from Amazon for around £3 >>>>
And this one from eBay for the amazingly cheap price of £1.50.
On another note, Britain has been blanketed by snow today!