While advice is offered to individual newcomers from time to time, I haven't seen a recent easily searchable DW thread that discusses introductory books across all the buddhist traditions so I thought I'd start one here.
I suggest each post contains only one or two books so a number of us can participate and that you say which tradition the book belongs to and briefly why you think it's good/helpful.
If someone suggests a book by a controversial buddhist figure by all means point this out but maybe attach a link to another thread rather than cluttering up this one.
Just as the trunk of an ordinary tree
Lying in the forests of the Malaya mountains
Absorbs the perfume of sandal from the moist leaves and branches
So you come to resemble whomever you follow.
~Patrul Rinpoche, The Words of My Perfect Teacher