AS A CHILD I began the habit of reading backwards the posters in the buses. It was fun, but it has yet to give me more insight than the price of pinto beans in Ecuador.

My guess is that Adrian Henri also spends much of his time reading transit ads. He may derive poetic insight from the habit, but what he has written down as poetry reads only like a backwards bus poster.

The book jacket of Tonight at Noon announces Henri as:

* A joyous synthesizer of all the arts, written, visual, and performing.

* A talented painter whose one-man show at the London Institute of Contemporary Arts includes his meat and salad paintings.

* A charismatic figure with a following that rivals film fan groups. His purpose, it tells us, is to discover "how far poetry can be pushed and still remain poetry." Henri has succeeded in pushing it no farther than the tip of his pen. He has little subtlety, less of the wholly honest examination of a private universe that is expected of the serious poet. He facilely manipulates external symbols and cliched concepts, a presentation masquerading as a penetration.

Mr. Henri has another approach to poetry though. He can take the obvious and turn it on its head. The result looks remarkably like the obvious turned on its head.

Tonight at noon

Children from happy families will be sent to live in a home

Elephants will fell each other human jokes

America will declare peace on Russia

World War I generals will sell poppies in the streets on November 11

The first daffodils of autumn will appear

When the leaves fall upwards to the trees

The last eighteen pages of the book are essays on topics ranging from Art (he likes it and tells us so in three thousand words too many) to Cliches (they should be given new I.D.'s and allowed a private life of their own). Mr. Henri's prose essays are reminiscent of the way a certain kind of professor talks. Henri drops names of books and artists with heavy distracting thuds, more to demonstrate his learning than to delineate his ideas.