Gamasutra was best for this w/r/t essays. GDCVault has a good selection of talks if you dig around. Re books, the Boss Fight book series (I think this is possibly what you alluded to) is generally of a very high standard, though the books are not just purely about development.

Edit: takes a bit more digging, but gamedev.net can be good for this. Particularly when there is a long running thread where a developer documents their progress -- the thread documenting the development of the "Return of the Obra Dinn" is the kind of thing I have in mind

Edit: wasn't gemdev.net, it was the Tig forums for Obra Dinn -- here's them collected on Reddit:

https://www.reddit.com/r/themakingofgames/comments/34qogp/_/