Terry Pratchett's Discworld Imaginarium
Over 200 gorgeous images. Some mere pencil sketches, others in beautiful living colour.
As a Discworld fan, you know you're going to buy it anyway. At £3.99, it's a decent price for an eBook - or £25 for a sturdy coffee-table book. Or go bananas (ook!) and splash out for the £100 signed limited edition.
The eBook is only worth reading on a laptop or tablet. Monochrome just doesn't do it justice.
But, that said, the images are frustratingly low resolution. The Bayeux Tapestry spoof is particularly hard to make out. And, while 200 images sounds like a lot - it is only a quick read.
One to ask for as a present, I think.