When in doubt get them a classic.
Though poetry is personal, it makes a nice present because it is a little bit like getting someone ideas more than words. and I find these Dover Thrift Editions very pretty. I like to get people many little things rather than one big item therefore it is very nice to get them several of these thin books. It also will widen your chances to please them.
If they are into literature and books, you can give them a bigger gift by getting them the complete works from a well-known author. They have some in nice editions and not always terribly expensive.
|Bright Star in Vintage Keats|
|Gramercy William Shakespeare |
For kids, following this same idea and remembering a gift to child can change is perception of the world, a beautiful book is very nice. I know many children enjoy their video games better so just get a video game & a book. Who knows? He or She might look at it one day.
Pick one with mesmerizing pictures and art. A kid will at least open the book to see the images.
For grown-ups, go for their favorite author and if possible, a beautiful cover and layout.
I highly recommend this Intégrale of SODA by Tome & Gazotti (even if it is in french)