Does anybody know of a book containing "all you want to know about the tetrahedron"? What you want to know should include basic geometry of the tetrahedron, study of orthocentric tetrahedra, the Monge point, various volume / edge length / face area formulae, volume via the Cayley-Menger determinant, the regular tetrahedron, etc.
The wikipedia page for "tetrahedron" is fairly interesting, but it will never treat things with the same level of detail as a textbook.