The site you quote from ( http://www.kingkong.demon.co.uk/ ) provides a list of abbreviations.

[a| = 'autobiography'
[b| = 'biography'
[d| = 'drama'
[e| = 'essays'
[f| = 'fiction'
[m| = 'music'
[n| = 'non-fiction'
[p| = 'poetry'
[s| = 'short stories'