Whoa... there's loads to choose from depending on just how much you want to spend, how you want to use it, and how "serious" you are.. but I guess you figured that!
I have 3 field guides, although in truth I use one much less often than others.
The one I use least is the Mitchell Beazley (I think written by Peter Hayman) I got when I joined the RSPB. They may still offer it, I don't know.
The two I use most are both Collins.
First the Collins Pocket Guide by Heinzel Fitter and Parslow (link...
http://www.amazon.co.uk/exec/obidos/ASIN/0002198940/qid=1126901116/sr=8-1/ref=sr_8_xs_ap_i1_xgl/026-0852576-5114861)
which I got about four or five years ago to replace it's predecessor.
The other is the Collins Bird Guide (link...
http://www.amazon.co.uk/exec/obidos/ASIN/0007113323/qid=1126901195/sr=8-3/ref=sr_8_xs_ap_i3_xgl/026-0852576-5114861)
which I also got free as it happens (when renewing my subscription to BirdWatching Magazine a couple of years back).
I use these in conjuction with each other, often taking both out with me - although usually only carrying one!
I think many members would suggest the latter is the better of the two, but they will also probably come up with their own suggestions.
You could also do a search on the forum, as there have been one or two discussions about the relative merits if a number of bird identification books, form pocket guides to the stonkingly good and arm-and-a-leg priced Lynx Edicions' Handbook of the Birds of the World. (
HANDbook...Ha!!! :eek!
All the best... :t: