A great starter book for electric flight is Bob Aberle's "Getting Started in Backyard Flying". Bob is a great resource of information and his latest book is evidence of that. It is sold at many places for about $25. [link=https://www.fmadirect.com/site/Detail.htm?item=1558§ion=27]FMA Direct[/link] is one of them.

For an on-line resource, the E-Zone's [link=http://www.ezonemag.com/pages/efaq.htm]Electric Flight FAQ[/link] is top notch!

Good luck!