The Era of simplicity, directness and honesty in cooking that has been heralded for some time may finally be upon us. At least that is the case if the better cookbooks coming onto the market this spring can be taken as an indication of popular taste.

As an example take (in fact, buy) Cooking Fish and Shellfish by Ruth A. Spear (Doubleday, $16.95). Fish, however costly it has become, has caught the public fancy. The timing of such a book is right and so is the approach. It is brimming over with useful infor- mation and wirtten in an informal but authoritative style that will bolster the cook's confidence.

A good deal of thought and care has gone into this volume as reflected in the chapter organization, the skillful drawings and a series of appendixes that include menu suggestions, shopping by mail and a list of fish and shellfishnames. Spear begins with general information, deals with techniques such as making broths, grilling and barbecuing. She breaks her subjects into categories such as saltwater fish and is contemporary enough to end with a chapter on "seafood sauces for pasta." a

No book will ever "tell it all" aboutthis vast subject, but Spear tells us more than enough. The recipes are well-presented, not overly complex and represent a nice blend of simplicityand sophistication. One minor quibble: references to sub-recipes within a recipe are indicated by only an asterisk without a page number. Thus, the cook has to go to the index, then on to the second recipe.

Another new book to seek out is an unpretentious work with an unpretentious title: american Home Cooking by Nika Hazelton (Viking, $14.95). Hazelton is a womanof considerable conviction and a talented writer. In a lively and stim ulating introduction, she tells the reader where she stands and avoids the pitfalls of pomposity or condescension in her survey of our national eating habits. "In this book," she writes, "i hope to prove that it is possible to produce good food with out everlasting fussing...The choice is a personal one."

Many of the recipes have familiar names; there is the expected sprinkling of regional fare. Similar creations can be found by wading through the plethora of regional cookbooks and church recipe collections that have been published in recent years. The advantage of "American Home Cooking" is that you ou have a single source of taste reference,and in Hazelton's case the sense of taste is a very good one indeed.

For those looking for entertaining reading between recipes this summer, Steven M. Weiss's contemporary tale, I Was a Food Writer for The C.I.A. (Chef's Catalogue,$9.95) should prove amusing and will provide an intriguing insight into the attraction of the restaurant business to young Americans.Weiss's C.I.A. is the Culinary Institute of America in Hyde Park, N.Y., where he was a student. The path to culinary greatness isn't an easy one. Weiss tells us of the formulation of his interest in food and cooking, of adventures that befell him between crib and kitchen. In the end, a slightly bloody ending worthy of a detective story, Weiss takes off his apron and directs his ambitions and obvious talent towardward journalism. Along the way he scatters laughs as readily as his colleagues resort to salt and peper.

Joan Chatfield-Taylor, who reported on fashion and other facets of style for the San Francisco Chroniclehas given an old subject some sprightly garniture in her book Picnics(Taylor &Ng paperback,$4.95). In addition to such now-familiar standbys as quiche and gazpacho, she explores "sandwiches for grownups" and a sequence of fairly ambitious main courses, begining with "leg of lamb with sorrel." Despite thechildren who adorn the cover photograph, most of the ingredients are on the sophisticated side (the recipes themselves are not complex, though). But she does include recipes for choco late chip cookies and brownies for kids of all ages.

Two new books on the foods of Mexico deserve attention. The first is Mexican Cookery (HP books paperback, $7.95) by Barbara Hansen. Hansen's articles on Mexican cooking written for the Los Angeles Times appear from time to time in this section. Her recipe style is concise, the directions are clear and truly exotic ingredients are rare. There is a basic glossary of chiles, their types, care and handling early in the book. Recipes range from drinks to desserts, with plenty of tamales and tortillas sandwiched between. The book is amply illustrated by color photographs and should prove a very useful addition to the library of cooks who want to dabble in Mexican cookery. u

Ido Romo's Homestyle Mexican Cooking (rand McNally, $9.95) is the work of an Illinois woman that grew from her cooking after marriage to a Mexican and visits to his family in GuadalajaraThere is no overview here, no attempt to analyze Mexican "cuisine." Instead, sincerity and enthusiasm set the tone for a succession of recipes, most of them simple and straightfford. The only mechanical aid Romo calls on regularly is the blender and, as with food in Mexican restaurants, she delivers a lot of recipes for the money.

Just in time for the fresh vegetable season comes a very stylish book, A Passion for Vegetables (viking, $12.95) by vera Gewanter. The subtitle is "Recipes from European Kitchens," and the author follows through with a wide- ranging sampler that, happily, doesn't isolate recipes by nationality but rather spotlights various types of preparation. Pasta and rice play a major role. Relatively obscure vegetables such as the cardoon are presented along with such standbys as carrot carrots and cabbage. Gewanter is a vegetarian, but the book is the work of a scholar and a cook of good taste. No trace of cultism or zealorty mars her presentation.

Elisabeth Ayrton's English Provin cial Cooking (Harper & row, $16.95) is a lovely addition to the limited literature on food folklore. But I suspect that collectors and cooking cultists will respond more eagerly than cooks looking for no more than some new recipes. Jugged hare, jellied game and mullet pie with clotted cream are fairly esoteric and a roast of young swan is out of the question.