Every knitter and crocheter needs a basic library with much needed information to refer to periodically.  I have listed some of my favorites.

150 Knitted Trims by Lesley Stanfield

101 Designer one-skein Wonders edited by Judith Durant

Anticraft Knitting Beading And Stitching For the Slightly Sinister by Renee Rigdon and Zabet Stewart

 Stitch'nbitch: The Knitter's Handbookby Debbie Stoller

Knitting Tips & Trade Secrets Expanded from The Taunton Press

Knit Aid rx for Knitters by Vickie Howell

150 Crochet Trims by Susan Smith

 200 Knitting Tips, Techniques & Trade Secrets by Betty Barnden

Vogue Dictionary of Knitting Stitches by Anne Matthews

Jelly Yarns by Kathleen and Nick Greco

Pop Goes Crochet by Vickie Howell

CraftHope:Handmade Crafts for a Cause by Jade Sims

The Knitgrrl Guide to Professional Knitwear Design by Shannon Okey (aka Knitgrrl)

The Perfect Finish: A No-Nonsense Guide to Finishing Techniques for Knitters of Every Level by Kara Gott Warner.

CALENDARS

365 Knitting Stitches A Year Perpetual Calendar

Martingale & Company

365 Crochet Stitches a Year: Perpetual Calendar

by Jean Leinhauser and Rita Weiss 

MYSTERY

Hooked On Murder -A Crochet Mystery

BOOKS FOR CHILDREN

 Kids Knitting: Projects for Kids of all Ages  by Melanie Falick