Which book would you take to your Desert Island?

"World Book Day is a celebration! It’s a celebration of authors, illustrators, books and (most importantly) it’s a celebration of reading. In fact, it’s the biggest celebration of its kind, designated by UNESCO as a worldwide celebration of books and reading, and marked in over 100 countries all over the world."

We read thousands if not hundred of thousands of words each week, job adverts, news items, press releases etc but most of us still find time to enjoy a chapter two of a good book.  
We love listening to Desert Islands Discs and like most people try to to work out which records we'd take with us.  Now for us that isn't as hard as picking which book to take along with the bible (or other religious tome) and the complete works of shakespeare.  
AW reads enough at work and will admit to being a slow reader, so she'd like to catch up on her backlog of Smallholder magazines! However, she reads a bedtime story to her two littlies every night and their current favourites involve frogs and frogs eating things, they are: Beware of the Frog by William Bee  (Is really good and a great surprising ending) also Tadpole's Promise by Jean Willis and Tony Ross (which again has a real surprise at the end, obviously it's not surprising when you've read it lots of times but great books). Both very apt for the next generation of CJS we thought! She says, "we would really miss books in general, can't do without the bed time story, how people don't read to their kids baffles me."
CMH decided to be a bear of very little brain but much courage and opted for the complete works of Winnie the Pooh, including Return to the Hundred Acre Wood by David Benedictus. Pooh can take her on expotitions and teach her all his hums whilst she digs into the philosophy of it all.
HB went down the tried and tested route of "I'll have loads of time so I'll finally get on with one I've never got on with before" and for her that's Lord of the Rings. She says, "as I've started it at least half a dozen times and never got past the first few pages, so if I'm alone on an Island I'd have a good chance of finishing it - or at least getting to the second chapter! I'm not one for re-reading books (other than children's and cookery books) so yes, that's my choice." She is the only person I know who read and cooks / irons at the same time, rattling through novels at an incredible rate!
TB in contrast takes her time and savours every single word, enjoying the pages of description and skill involved in putting together strings of words in poetic harmony.  Again she's thinking of time so has gone for a long book, one that by the time she's finished it she'll have forgotten the beginning and it's Sarum by Edward Rutherford (we both recommend this one, even if you only read the beginning (like I did - too many words for me) it's an incredible story).
My list started with ten, grew to over twenty and then was narrowed down to two and unlike everyone else mine are not works of fiction, I struggled between the complete Encyclopedia Britannica and the Annotated Ultimate Alphabet.  After much consideration (along with a bit of ribbing that I have enough useless information in my head) I went with the picture book, it's called the Annotated Ultimate Alphabet by Mike Wilks  and is a series of wonderful drawings, one for each letter of the alphabet with over 300 As alone. It's another one we'd all recommend, having left mine in the office to be poured over The Team coffee breaks have been filled with "What's that breed of horse then?" and "Why is there a tight-rope walker on the E page?" (Equilibrist  was the answer).

Which one book would you love to have the time to enjoy or simply couldn't bear to leave behind? - it's harder than you think!