This PDE text by Haberman covers the ideas about separation of variables, Sturm-Liouville problem, finite difference numerical method, Green's function, Fourier transform, Laplace transform, and the method of characteristics. It presents the materials in quite plain, detailed manner. To me, the best part of this book relative to another books is that of Green's function. I've read Arfken, Farlow, and Strauss's texts, but have never got a satisfactory understanding.
The Strauss's one is the worst. To a beginner or non-mathematician, it is impossible to accept that kind of crazy things. The Farlow's one doesn't pay enough effort on this topic. It just goes through in a few pages. The Arfken's one (Mathematical Methods For Physicists) gives a concise presentation in quite physical way, but not for beginner. It is more like a summary.
Haberman introduces Green's function in his book with two chapters and in a quite different manner. He doesn't, like most physicists do, introduce it by Poisson's equation, but by heat equation and Fourier series; the ordinary definition of Green's function with delta function is given later. Though I think this is not a good idea and the presentation is not good, I do agree that it is much easier for beginners to understand. He makes no haste going into the three-dimensional case. Instead, he works on one-dimensional cases, then two and three-dimensional cases systematically. The point is, I think this won't make it too mathematical like the Strauss's one or too physical so that it is too constricted. In addition, he derives Green's functions in deductive way, instead of only taking a look at the physical suggestions. This makes the results convincible and gives readers a more comprehensive understanding.
Perhaps the most annoying thing of this book is that it is too wordy. However, this may be another advantage-the text is hard not to understand!
Someone says that Haberman hardly works on subjects other than heat equations. That kind of comment is misleading. He does work on wave and Laplace's equations. He just use heat equation as a main thread.
If you're learning PDE for physics or engineering or other applications, this book is quite suitable for self-studying. If you only want to study the most basic ideas about PDE, then Farlow's may be a light choice. If you want to study more, you can read Haberman's text.