ID Books: Recommendations

So, over the years my friends and family have always asked me which ID books I'd recommend, particularly to take out into the field. I've used several books for wild flower and bird ID, and since college I have not had any doubts about which I prefer.

For wild flower ID, I'd suggest using keys.. flower ID can be so complex and having a systematic approach makes it much easier. I always rely on a combination of two books: 

John Hayward - A New Key to Wild Flowers
Francis Rose - The Wild Flower Key 

 To ID to a species level (you'll need a hand lens in many cases) I usually start with the Hayward key.. I have a 1992 edition I bought from Amazon Marketplace secondhand (shown in the link), but I believe the Field Studies Council republished it in 2004. I then use Rose to double check. Neither book is pocket sized, but are also no trouble to carry in a rucksack.

There are an overwhelming number of bird ID books and I must have tried six before I settled with this series. This is the most recent edition as far as I am aware, but its always changing. Every species has an entire page to itself covering identification, habits, voice, habitat, food, breeding movements and migrations, population, conservation and distribution (with colour-coded maps). The multiple pictures (including in-flight) are beautifully hand drawn, making the book just generally nice to thumb through. The only dissapointing element of this book is that it doesnt cover bird eggs, but I have another book I refer to for this, though it is too big to take out with me, so I rely on photos or collecting broken specimens.

RSPB Handbook of British Birds

I would love to hear your suggestions on ID books, particularly on butterflies and moths. Everyone has a preference and it is always nice to have options.