The new prodigy electronic information service has pulled off an admirable technical feat.

Available for a flat $9.95 a month to anyone with an IBM-compatible computer and a modem, the new joint venture by Sears and IBM is a simple, friendly and colorful information and shopping service aimed at a market of upscale users who have technology at their disposal but not much time for chores.The question is whether Prodigy packs enough horsepower to keep people interested once they lose their infatuation with its graphics.

While Prodigy has a few outstanding features, my initial feeling is that the service is a mile wide and an inch deep. It offers a little bit of everything and not much of anything. Beneath the veneer, it is a shopping mall financed by advertisers.

To understand Prodigy, consider what makes it different from its big-time competitors, such as Compu-serve, The Source, Genie and the Dow Jones News and Information Service.

Most of these services charge users by the connect hour. The longer they keep you on, the more money they make. Prodigy, on the other hand, charges a flat monthly fee that is far lower than the cost of providing the service.

Prodigy hopes to make its money from advertisers, whose colorful promotions show up at the bottom of every screen. The ads are tailored to the user, who fills out a profile when he signs up. If a man might find a lot of automobile ads, a woman will find more fashion ads.

If you are interested in an advertisement, you can delve further into it and receive screen after screen of information and pictures. In many cases, you can order products on line and have them charged to your credit card.

It is the interaction between users and advertisers that makes Prodigy tick. So it offers enough to keep you interested for a while but not enough to tie up substantial amounts of expensive computer and telephone time.

The service is divided into three parts, or "buildings" - information, shopping and living.

Information is definitely a bit thin. For example, Prodigy's news consists of a dozen brief but well-written summaries of top stories. Compu-serve, by way of contrast, offers the entire Associated Press Datastream service, while Dow Jones offers its own news service and the full text of the Wall Street Journal.

If you want financial news on Prodigy, daily stock summaries (with a cute Dow Jones graph) are available. You can even store a list of stocks and get the latest quotes. But the list is limited to a dozen stocks, and the information is only of the high-low-close variety. Other services, for a price, offer serious investors a wide array of financial information, which can be stored on your disk in a format compatible with the popular Lotus 1-2-3 spreadsheet.

For youngsters, Prodigy offers a number of on-line games, including quizzes and a version of the popular "Where in the World Is Carmen San-diego?" detective program.

But most of these offerings are like old movie serials - to get to the next step you have to wait till next week. This means nobody is going to spend a lot of time playing. On the hourly services, the games are designed to hook you and keep you hooked for as long as you want to play - and pay.

Another example is electronic mail. Users can send messages, but they are limited in length. And there is no way to chat with other users on line, as there is with most services.

There are a couple of features that may keep people coming back. For travelers, Prodigy offers the first friendly version of an airline information and reservation system I've seen.

It connects you with American Airlines' Eaasy Sabre service. Prodigy officials say they spent a year developing software that makes it easy to find information and book reservations, and I can believe it.

Most other on-line services offer airline reservations information, but they are difficult to use, and there is frequently a surcharge.

Prodigy's version of Sabre offers not only flight information and reservations but also bargain-fare information, including restrictions. For frequent flyers, this is a terrific deal.

Likewise, Prodigy is making arrangements with financial institutions in each city to offer on-line banking. Unlike some on-line banking services, which will handle only electronic fund transfers, some of Prodigy's banks will also mail out checks (this may vary by locality).

There is an additional fee for on-line banking, but in many cases it is only slightly more than the postage that you would pay to mail checks yourself. Once again, a real convenience.

So Prodigy is definitely a mixed bag. It is easy to use and visually stimulating. For travelers, people interested in on-line banking and casual investors, it may well be worth the relatively small price.

On the other hand, there isn't much that really interests me. The news and information is paltry at best. Certainly there's nothing that would make me cancel my membership in the hourly services. You get what you pay for.

And even though I'm a computer junkie, I can't see any reason to use one to log onto a service and order from the Sears catalog when I can pick up the phone and do the same thing while I'm drinking my coffee.

Likewise, I already have wonderful bill-paying software. She's user-friendly and neither of us sees any reason to replace her with a computer.