My letter grade system:

A = Outstanding. Highly recommended.

B = Very good. Occasionally has problems with proportions, ingredients, or technique, but successes greatly outnumber failures.

C = Has some good recipes, but also suffers from a great number of problems. Often can be more trouble than it's worth to try to cook from.

D = A disaster. Failures greatly outnumber successes. Not recommended.

F = Not a single successful recipe to be found. Avoid at all costs.

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Food Network Favorites: Recipes from Our All-Star Chefs, Food Network Kitchens, Jennifer Darling (Editor). (Full review coming soon.)
Suffers from the usual problems: poor editing, weak instructions, occasional errors with ingredient amounts or usage. Many of the recipes can be found in the individual chefs' other books. Bottom line: not a necessary addition to a well-stocked kitchen library. B-/C+

Off the Shelf: Cooking from the Pantry, Donna Hay. (Read the full review here.)
Very good ideas and interesting combinations of ingredients. Frustrating at times because of a casual attitude towards instructions and technique. Worth having, but the instructions need to be carefully reviewed before getting started on a recipe. B-

Sara's Secrets for Weeknight Meals, Sara Moulton. (Read the full review here.)
Very problematic, with weird combinations of ingredients, poorly-thought out instructions, a lack of photos, and some outright failures. Here and there it has a good recipe, but there are too many bad ones. C-

Everyday Italian, Giada De Laurentiis. (Read the full review here.)
A handy basic Italian cookbook with some excellent recipes. Occasionally suffers from sloppy technique and editing. B+

Fast Food My Way, Jacques Pépin. (Read the full review here.)
An outstanding book. Excellent recipes, clear instructions, creative ideas. The introductory chapter and dessert chapter are worth the price alone. A

Jamie's Dinners: The Essential Family Cookbook, Jamie Oliver. (Read the full review here.)
Very creative with strong ideas and tasty food. Fails in its accessibility; too often vague and sloppy when it comes to instructions and technique. For experienced cooks: B+. For kitchen novices: B-

Live, Love, Eat!, Wolfgang Puck. (Read the full review here.)
A good introduction to Wolfgang Puck's cuisine. Occasionally suffers from "restaurant-chef-itis," with too many hard-to-find ingredients or fiddly technique. Very good results if you're willing to put in the time and effort. B+

30-Minute Meals 2, Rachael Ray. (Read the full review here.)
A better book than 30-Minute Get Real Meals, but not without problems. Italian recipes are good, everything else is risky. C+

30-Minute Get Real Meals, Rachael Ray. (Read the full review here.)
An attempt at low-carb cooking that's not satisfying to anyone, with serious problems in technique and bizarre proportions. A few good recipes bring the grade up to C-