O'Reilly just published an updated edition of their bestseller on Bitcoin technology, "Mastering Bitcoin," earlier this month.[1]

For a more general/conceptual understanding of blockchain technology and its applications, including non-cryptocurrency applications, "Blockchain Revolution" is a good read.[2]

[1] Mastering Bitcoin http://amzn.to/2uewdK9

[2] Blockchain Revolution http://amzn.to/2vniXSf