I haven't read this yet, but I noticed it's currently free on Amazon.com for the kindle version of the book Hello, Bento! - A Collection of Simple Japanese Bento Recipes
No idea if this is a long term price, so might as well grab it while it's free.
If you don't happen to have a kindle, you can still 'buy' this free book and read it through the Amazon Cloud Reader, which allows you to read books on your computer, phone, &c.
When I have a read of it, I'll let you know what I think. I find a lot of bento books, especially the ones compiled by Westerners, tend to be hit and miss.