The other day with a hook order I received a copy of the booklet; “How to Choose and Use Fly-tying Thread”, by Paul C. Marriner. It is a booklet put out by UNI and sells for $3.00 although I got mine for free 
.
It has a description of different thread types and construction, bobbins and really good descriptions and photos of different thread techniques. I found it to be worthwhile and maybe some of the beginning to intermediate tiers might as well, especially for free or $3.00. I’m sure lots of this stuff is covered in newer tying books but I haven’t bought a how-to fly tying book since Indian necks were the pinnacle.
I got mine from Lines End but I’m sure lots of UNI products dealers have access.
[url=http://www.linesend.com/:f7404]http://www.linesend.com/[/url:f7404]
The UNI booklet is on their Sponsor page here at FAOL, and has been for several months.
<BLOCKQUOTE><font size=“1” face=“Verdana, Arial”>quote:</font><HR>It is free of charge to qualifying recipients. The Federation of Fly Fishers, United Fly Tiers, Trout Unlimited Canada, and the Fly Dressers Guild (UK) have all agree to distribute the publication in appropriate numbers to instructors.
If you are a fly-tying instructor not belonging to any of the mentioned organizations you can request copies from info@galesendpress or by writing to
Gale’s End Press, RR #1, Mahone Bay, NS B0J 2E0, Canada. Please include the average yearly number of students!<HR></BLOCKQUOTE>
Check out the Sponsor page - you might be missing something! 
[This message has been edited by LadyFisher (edited 20 October 2005).]
LF:
Duh!
I even did a search before I posted this to see if it was covered but forgot to check there.