Vivid writing on gastronomy by author of ''Three Musketeers''

Referring to Alexandre Dumas's ''Grand Dictionnaire de la Cuisine,'' Waverly Root, in his own dictionary entitled ''Food,'' has called Dumas ''an author more picturesque than accurate.'' That may well be true.

But Dumas generously compensated for his inaccuracies and inconsistencies by giving us a highly entertaining feast, even if it is hard to digest in its entirety.

Better known for ''The Three Musketeers'' and ''The Count of Monte Cristo,'' Dumas pere brought the same imagination and color to his mammoth culinary treatise.

He was a fascinating person, so it is not surprising that his dictionary makes fascinating reading. All of his writing was filled with the same irrepressible eagerness for living fully.

At home or traveling, he seems to have had a gift for attracting - and keeping - interesting friends. But throughout his life, to balance the flamboyant side of his nature, he worked hard and produced a tremendous work.

In his entry on Cavaillon Melon he writes, ''The reader may presume that the town of Cavaillon is not mentioned here, because of its situation on the river Durance, nor for its proximity to Avignon, nor for its triumphal arch, but for its famous melons,'' which he favored above all others.

One day he received a letter from the city council of Cavaillon asking him to send two or three of his favorite novels for a new library it was establishing.

''Now, I have a daughter and a son, whom I think I love equally; and I am the author of five or six hundred volumes, and believe myself to be just about equally fond of them all,'' he confides to the reader.

''I consequently proposed to send to the town of Cavaillon a complete set of my works,'' he continued, ''if the municipal council would be willing to vote me a life annuity of twelve green melons.''

Twelve years after the exchange of letters, Dumas wrote, ''The municipal council of Cavaillon replied by return of post that my request had been unanimously endorsed, and that I would certainly receive my life annuity, which in all likelihood is the only one that I will ever have.''

The entry was finished with the hope ''that the people of Cavaillon will always find my books as charming as I find their melons.''

Dumas's ''Dictionnaire'' was first published in 1873, three years after he passed on. He had planned to write it for many years, but only when he was in desperate financial need did he finally finish it.

Unable to check facts and sources, he delivered the long and disorganized manuscript to his publisher shortly before his death in 1870. No one seems to have put it in order, either for its initial publication or any other edition in the century since, until now.

Alan and June Davidson recently undertook this formidable task. Besides organizing the unwieldy original, they have selected the best parts and translated them into English for the first time.

Their result, ''Dumas on Food,'' was published in London in 1978 by Michael Joseph, and the American edition has just appeared (Prospect Books, $17.50, distributed by the University Press of Virginia).

The Davidsons have reorganized the 1,200 pages of the original 1873 edition into 300 pages, as they tell us, ''all with the aim of extracting the real Dumas , like silver, from the dross in which it is embedded.''

Their preface discusses the difficulties they faced, precisely what they have done, and why. An introduction provides background on Dumas's life, his work on the ''Dictionnaire,'' and the problems surrounding its publication both then and now.

Their glossary informs us of what Dumas would have assumed his 19th-century French readers knew about the kitchen.

The dictionary itself is rearranged alphabetically by English titles, with the original recipes ''ruthlessly'' selected, as the editors put it. Two appendixes follow, one of which gives contemporary accounts of Dumas as a cook. All of this is absorbing, but not nearly so much as the ''Dictionnaire'' itself.

Dumas's entries can be long essays, such as the one on mustard which was originally an appendix incorporated by the Davidsons into the dictionary. It is an early and amusing description of competitive marketing techniques - and an example of advertising on Dumas's part.

His entries touch on politics, history, philosophy, myth, and nutrition.

Even when his information is ridiculous, it is no less entertaining, such as the chicken in China, of which he states, ''Instead of feathers, it has wool.''

Sometimes it is so true as to be aphoristic: ''Everyone recognizes the smell of garlic, except the person who has eaten it and who has no idea why everyone turns away when he approaches.''

''Dumas on Food'' is well produced, handsomely illustrated with engravings from 19th-century French culinary books, and provided with corrections and comments by the editors where needed. And at last it is accessible to English readers.