Good Books on unusual white openings

This section is not quite my cup of tea, but one I can recommend is Der Linksspringer 1.Sc3 by Harald Keilhack. I suppose that this is the kind of opening that won't make sense to you unless you've tried & enjoyed 1.e4/d4 Nc6!? Keilhack has written a very thorough tome on this opening. A lot of ideas to choose from, unfortunately you need to understand german quite well - but that's easy to remedy as there is an english version too!