LevelDB is amazing, and it represent a new trend in the whole NoSQL space: build your own database. Thanks to a small core, you can build just the data store you want and need. This book teaches you how, ignore it at your own peril.
I started tinkering with LevelDB last April, after I heard the amazing NodeUp podcast about it. Not much later I wrote LevelGraph, a graph database on top of LevelDB, and I became a LevelUp's committer -- LevelUp is the node.js high-level API for LevelDB. What all this relates to this book? I wish I had this book when I started, as it explains how to use the C++ binding of LevelDB in a hands-on way, something I had to figure out myself.