I get some lovely books from The Book People, they sell huge amounts so know what is popular and often have sets at very low prices.
Usborne's board books are good too, 'Baby's First Toys Book' is far less bland than the title implies!
Rod Campbell's books are lovely, some Touch-and-Feel, some with flaps.
My GC liked board books of Hug! The Hungry Caterpillar, Ten in a Bed, Incy Wincy Spider (includes furry spider!!), Going on a Bear Hunt, Peepo!. Also Dorling Kindersley's 'Baby Faces Peekaboo! a late format board book with big flaps and a 'mirror' in the back.
Five Little Ducklings and a similar book with touchable ladybirds are good for counting.
Have fun choosing, I do!