Years ago (way back in 2013) I wrote a blog post which compiled some links to ambisonics resources on the web (http://versed.com.au/some-ambisonic-resources), but there has been a huge increase in interest in ambisonics in the world due to the various applications of it for Virtual Reality and 360 video etc. There is now a free Creative Commons (Attribution) book available from Springer Open that goes into the theory of Ambisonics which might be a good read for those serious about understanding it more. You can access the book at:
