Here is the lovely book that led us through our homeschool Bible time this past year:

There were several times when I was either stunned or moved or both by how clearly and helpfully some difficult concepts were explained. Of course, the true test of a good "school" book is if the kids will read it outside of school - and they did!
Add in a memory verse each week, and Bible time it sorted. Obviously, though, this would serve very well to help lead through family devotions or even for a curious kid to read through on his or her own.
I hereby recommend it! So do these people...