"Man's Search for Ultimate Meaning" by Viktor Franl, is a good book for understanding the basic differences between varying schools of psychotherapy, and how logotheraphy fits today's society. While the book covers some of the basic precepts of logotheraphy, it is not designed as an introduction, but more of an expansion, particularly the concept of unconscious religion. My recommendation would be to begin with "Man's Search for Meaning" by Viktor Frankl before reading in order to understand more of his primary assumptions. As with many books of this kind, more lecture and educational paper than produced for mass market appeal, the book can be slow and tedious in spots (I had to look up more definitions of words than anything I have read since college); however, its golden nuggets are well worth wading through the jargon, interwoven definitions, and psych-speak.
Thoughtful follow up to his Halocast memoroire