Indeed, you might not find a book exclusively treating only the harmonic oscillator, but almost any QT textbook will cover this topic. It's the one simple model that can be solved completely and analytically for all kinds of problems, and it's a very fruitful endeaver to do this. The best thing is, you can do it yourself, and it's big fun: I'd suggest the following sequence of study:
Harmonic oscillator in 1 dimension
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(1) starting from the Heisenberg algebra for position and momentum, define the "ladder operators" for the energy eigen values and derive the complete spectrum and energy eigenbasis in representation free form. Look at this in the Schrödinger and the Heisenberg picture of time evolution.
(2) Work out the wave functions in terms of the position and momentum representations. You'll learn a lot about Hermite polynomials and techniques to handle orthogonal polynomials in general (Rodrigues formula, integral formulae etc.)
(3) Try to get the propagator in the position representation in two different ways: (a) use the just elaborated energy eigen functions and derive the corresponding series. With help of the integral representation of the eigenfunction you can even do the sum analytically, but that's tricky and you should look for it in textbooks and online material; (b) use the Heisenberg picture and solve the operator equations of motion for the position operators and then evaluate the propagator as
$$U(t,x;t',x')=\langle x,t|x',t' \rangle.$$
(4) Derive coherent and squeezed states as the eigen functions of the annihilation operator.
Harmonic oscillator in 2 and 3 dimensions
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(1) Show that the harmonic oscillator in 2 and 3 dimensions in cartesian coordinates is simply given by the three non-interacting 1d harmonic oscillators; i.e., the harmonic oscillator has a pretty large symmetry group which goes beyond the space-time symmetries (dynamical symmetry).
(2) Using the annihilation and creation operators to show that the symmetry groups are SU(2) and SU(3) respectively (for an n-dimensional oscillator it's SU(n)). This gives a great way to derive all the irreducible representations of these groups (see Sakurai, modern quantum mechanics).
(3) Solve the energy eigenvalue problem by separation of the time-independent Schrödinger equation in polar and spherical coordinates (for the 2D and 3D case, respectively).