I find that looking at other's people's stuff gives me ideas of what I might want to do.

Several books that always bring me back to Paris are:

"Le Notre's Gardens" by Michael Kenna

Atget Paris" from Gingko Press

"Brassai From Surrealism To Art Informel" from Fundacio Antoni Tapies

There is this strange artifice you find among photographers that we must never repeat the work of others but only find "our own true vision." This is mostly nonsense. In looking at great work, you will find inspiration for your own (not to mention really feeding you own soul).