What books do you recommend to learn spindling?

Spindle Spinning books in print ....

Spindle Spinning: From Novice to Expert (Connie Delaney) -- covers many kinds of spindles, in good detail, focus on how to spin on them
Spin It! (Lee Raven) -- taken from her earlier work Hands On Spinning, focus on spindles; also covers hand carding. Great update on the photographs within
Spinning In The Old Way (Priscilla Gibson-Roberts) -- I think this replaces her earlier High Whorling; covers top whorl spindle spinning
Spindling: The Basics (Amelia Garripoli) -- top whorl spindling and a FAQ on a variety of topics including fiber preparation and fiber tools (that's me!)
A Handspindle Treasury (Spin-off Magazine) -- collection of spindle articles from the magazine
Handspindles (Betty Hochberg) -- covers spindle types more than techniques

And there's a great video, Spindling Around the World (Barbara Clorite), which covers a wide variety of spindle types and how to spin them.

There are also websites with complete instructions:
http://www.interweave.com/
http://www.icanspin.com/
http://www.mielkesfiberarts.com/spndl_inst.htm
http://fibervilleusa.com/mall/lollipops/spininst.htm

It's possible there are more books still in print, that's my "core" set. Most of the (wheel) spinning books will also discuss spindle spinning, too.