Best book about the teachings of the original Buddha and the early Buddhist texts?

I am looking for some book recommendations on scholarly reconstructions of the Early Buddhist Teachings/Texts and the teachings of the original Buddha. E.g. some scholars say that kamma didn't have a major role in early Buddhism, or they say that some other things that are considered a part of Buddhism didn't exist back then or weren't taught by the original Buddha. So I'm looking for a book that talks about this and tries to reconstruct the teachings of the original Buddha in the most authentic way.