What's the opposite of smut? 'How Life Is Handed On' by Cyril Bibby.
A sex education book published in 1946, it's hugely tasteful and sensible from its title downwards. It covers all it needs to cover in an informative matter of fact way. It doesn't shy away from using the word vagina, though, nor does it pretend 'night loss' doesn't happen to adolescent boys. It really is a paragon of tasteful educational virtue and, as such, is almost no fun at all.