There's a suggested roadmap for reading it, too: http://www.reddit.com/comments/63hth/ask_reddit_which_oss_co...
It is written in ruthlessly standard ANSI C (for maximum portability).
It will probably also complement your C -- it's intended to be a handy drop-in scripting language to embed in C programs, though it's also a pretty cool language on its own merits. They had an unwavering focus on keeping it clean and very small for embedding, and they make some really interesting choices along the way. It's sort of like a minimalistic Python; it gets a lot of power out of using "tables" (rather like Python dictionaries or Perl hashes) as a primary data type.
One thing I think helps you become a better programmer, is to read your own code carefully a long time after you have written it.