Bookstores --
Check out Crawford Doyle, Madison Avenue in about the 80's I think, sorry short of time to Google right now but you should be able to find it pretty easily. Nice selection of collectible and out-of-print books, prolly more expensive than the Strand but less than places like Bauman, several blocks down on Madison and Ursus Books in the Carlyle Hotel.
There's also the Argosy Bookstore on E. 59th Street, near Bloomingdale's, sort of similar to the Strand.
Pizza --
A great value in the by-the-slice scene is NY Pizza Suprema, 413 8th Ave bet. 30/31st Streets. Come out of Penn Station on the 8th Avenue side and it's just across the Avenue.
But IMO the very best pizza in NYC isn't in Manhattan -- it's called Forno Sciliano and is in Astoria, Queens. If you don't need instant gratification, take the N train to the last stop, Ditmars Boulevard, and walk about 10-15 minutes. Again, Google it and you'll see the website. If you go, the Quatro Staggione isn't to be missed. Their food that tastes more like what I had in Italy than almost anywhere I know of, and their wine list isn't too shabby either. Not trendy at all, caters to regulars, but worth seeking out.
Enjoy your trip.