I'm a great believer in Heavy Metal banjo, myself.
Seriously though, I have seldom found "Tutor" books much help. They are either so simple that they don't tell you anything or so complex that they don't make any sense.
You can learn much more and more quickly from a real person.
As for sight reading, a large proportion of banjo music gets written down as Tab (tablature) which notes the finger positions on the strings for each note. If he reads standard notation, he may need to learn an alternative system.
A good place to visit with your questions is a site called the Banjo Hangout- BLICKY.
Or try this one - Banjo L .
Quack!
Geoff the Duck.