Tom Waits' music career spans over four decades and covers a wide range of genres, including blues, jazz, rock, and experimental music. He has released 19 studio albums, numerous live albums, and several collaborations with other artists. His back catalog can be daunting, but there are a few albums that are considered good starting points:

1. "Closing Time" (1973) - Waits' debut album is a great introduction to his early singer-songwriter style. The album features songs that are more mellow and introspective than his later work.

2. "Rain Dogs" (1985) - This album is often considered one of Waits' masterpieces. It is a diverse collection of songs that blend rock, blues, jazz, and experimental music.

3. "Swordfishtrombones" (1983) - This album marked a significant change in Waits' musical style, moving away from his earlier piano-based sound and incorporating more experimental instrumentation.

4. "Mule Variations" (1999) - This album features some of Waits' most accessible and memorable songs, including "Hold On" and "Get Behind the Mule."

5. "Bone Machine" (1992) - This album is a dark and experimental work that showcases Waits' unique songwriting and vocal style.

Ultimately, the best starting point for Tom Waits' back catalog depends on your musical tastes and preferences. You may find that you prefer his earlier or later work, or that certain albums resonate with you more than others.