One of my best buys was Delia Smith's Illustrated Cookery Course, in the special (small) BCA format. It's been one of the best things I ever bought, and I use it all the time.
Yesterday, my 28 year old copy fell apart. Literally. It's already been taped together numerous times, and yesterday it fell into pieces. (Spookily, one of the pieces was at the recipe for Ossobuco which was exactly the recipe I was looking for, but I digress.).
I picked the pieces up, and the pieces fell into pieces. I thought about taping it up again, but I realised that I was just putting off the inevitable.
I've ordered a new copy. Paperback this time, and normal sized.