Geometry

Blood Lines by Tanya Huff
BloodCircle by P. N. Elrod
Blue Corn and Square Tomatoes: Unusual Facts About Comon Vegetables by Rebecca Rupp
Gate of Darkness, Circle of Light by Tanya Huff
Sphere by Michael Crichton

Will the circle be unbroken?, by Studs Terkel
Tales of Times Square, by Josh Alan Friedman
The Line of Beauty, by Alan Hollinghurst
Octagon : Being an account of a famous Washington residence, by George McCue
The Papers & the Papers: an Account of the Legal and Political Battle over the Pentagon Papers, by Sanford J. Ungar

The Cone-Gatherers by Robin Jenkins
The Caucasian Chalk Circle by Bertolt Brecht
Napoleon's Pyramids by William Dietrich
Callander Square by Anne Perry
Bedford Square by Anne Perry

Flatland by Abbott
The Fourth Dimension by Rudy Rucker
The Insider's Guide to the Triangle (i.e., the Research Triangle--Raleigh, Durham, Chapel Hill--amazingly enough, no touchstone)
The Turning Point by Fritjof Capra
Proof by Dick Francis

Washington Square Henry James
Getting High in Government Circles Art Buchwald
The Human Angle William Tenn
Area of Suspicion John D. MacDonald
The 42nd Parallel John Dos Passos

The End of the Line
The Life of Pi Somebody was bound to say this!
The Tipping Point
The Inner Circle
Longitude by Dava Sobel

Angle of Repose by Wallace Stegner
A Circle of Quiet by Madeleine L'Engle
The Cricket in Times Square by George Selden
Peripheral Visions by Phyllis Theroux
The Dot and The Line; A romance in lower mathematics by Norton Juster

The Outline of History
The 64 Square Looking Glass
The Tao of Physics: An Explanation of Parallels Between Modern Physicals and Eastern Mysticism

Only 3 :(

Remember Me to Harold Square by Paula Danziger
Mrs. Pollifax and the Golden Triangle by Dorothy Gilman
Pentagon: A History: the Untold Story of the Wartime Race to Build the Pentagon by Steve Vogel
Blast Radius by Don Pendleton
Straight Man by Richard Russo

Q-Squared by Peter David
Closed Circle by Robert Goddard
Cubes, Cones, Cylinders and Spheres by Tana Hoban
Vanishing Point by Morris West
Area 7 by Matthew Reilly

Sphere Of Influence - Kyle Mills
The Sewing Circles Of Herat - Christina Lamb
Vicious Circle- Robert Littell
Angle Of Repose Wallace Stegner
Parallel Myths - J.F. Bierlein

Gridlinked by Neal Asher
Crystal Line by Anne McCaffrey
N-Space by Larry Niven
The Zenith Angle by Bruce Sterling
Slant by Greg Bear

The Life of Pi Yann Martel
The Tenth Circle
Less Than Zero Bret Easton Ellis
Finite and Infinite Games James Carse
Flatland Edwin A. Abbot