I started learning Common Lisp, but ASDF and Quicklisp threw me off. I couldn't tell if you were supposed to choose one or the other or they were used together. This might revive my interest in Common Lisp if I get around to reading it. But in the meantime I drifted off to Racket, which is relatively well documented and has extensive libraries and really unique features.
The packaging story in common lisp is.... Not great.
It's hamstrung by archaic naming conventions that confuse newcomers. What CL calls a system is roughly analogous to what most other languages call a package. What CL calls a package is what other languages call a namespace.
Despite all that it's a pretty good language if you can find libraries for what you need. The de facto standard implementation (sbcl) has a very good compiler and an acceptable GC. The language itself is expressive and it makes for very quick and pleasant DX. I love writing common lisp.
For anybody who's still confused, the tl;dr is ASDF is the actual package loading mechanism, Quicklisp doubles as an ASDF wrapper and a package manager.