"Dinosaurs on the Roof" by David Rabe; Simon & Schuster Adult Publishing Group

There are a number of terrific ideas rattling around in David Rabe's cavernous new novel, "Dinosaurs on the Roof."

Unfortunately, they're ideas that — properly honed and focused to an appropriate scale — probably would have made a fascinating play. In a sense, that's not surprising, as Rabe, 68, is an important American playwright and sometime screenwriter, best known for the powerful dramatic trilogy inspired by his service in Vietnam — "Sticks and Bones," which won the 1972 Tony for best play; "The Basic Training of Pavlo Hummel," which earned the Obie for distinguished playwriting; and "Streamers," which picked up the New York Drama Critics' Circle award for best American play of 1976.

"Dinosaurs on the Roof" is nothing if not ambitious, with an intriguing formal structure. The entire narrative occurs on a single day in the small Iowa town of Belger. Rabe is an Iowa native, and any novelist who elects this particular narrative approach puts themselves in the shadow of the great modern novel, "Ulysses," in which James Joyce reconstructed a single, specific day in the history of his native Dublin, but also the inner lives of his characters within that history.

Rabe seems to have had something similar in mind with his two female protagonists, Janet Cawley and Bernice Doorley. Their paths intersect early one morning as Janet returns from another of her solitary jogs. She is divorced, a schoolteacher who has quit her job and made an occupation of cutting herself off from the world behind a scrim of exercise, alcohol, drugs, books, TV movies and sex with unavailable men. Bernice, a much older woman, was the best friend of Janet's late mother. She arrives to receive Janet's reluctant hospitality — tea and cookies — with a request. Bernice belongs to a fundamentalist church whose members expect to be taken up in the rapture — that is, bodily assumed into heaven in anticipation of the world's end — that very night. She needs somebody to look after her dogs when she's gone. Hence, a rather promising bit of dialogue:

Janet acknowledges that she's read about the rapture in Time or Newsweek, but "at the time I didn't know it pertained to Belger."

"Well it pertains to some of us, anyway, and it's coming tonight."

"Tonight?"

"I'm afraid so. Which is why I'm here as you can imagine."

"Tonight? Are you sure?"

"Of course I'm sure. That's the whole thing, because it's pretty well set I'm one of them. I'm going to be one of the saved. So you see, I'm worried about my animals."

"Is something going to happen to them?"

"Well, for Pete's sake Janet, just use your brain for a second. I'm not certain exactly how it's going to work, but once I am taken up and I'm gone, they're going to be there in that house all alone."

In other words, Bernice, estranged from her daughter, Irma, has arrived hoping that Janet will feed and walk her dogs after she's assumed into heaven.

So far, so promising.

Then, problems begin to arise. The narrative unfolds as Janet and Bernice each reflect on their lives and emotional histories. Each seems meant to stand for a particular American sort of escapism: Janet, the atomization of hedonism or, more colloquially, sex, drugs and rock 'n' roll, and Bernice, the escapism that is fundamentalist religiosity with its equally narcotizing collective self-delusions. Fair enough, but Janet and Bernice are so singularly joyless in their pursuit of self-obliteration that you begin to wonder why they bothered.

These are, in other words, two singularly unsympathetic protagonists. That gives rise to a second problem, which is that they go on about themselves at wearying length.

More troubling is a certain lack of emotional authenticity in a book that sometimes seems to aspire to be the first "Chick Lit" novel of ideas. Janet's drive to suicidal oblivion never seems quite real and, while her memories of sexual liaisons past seem convoluted enough, they're hardly the stuff of this self-lacerating torture. Similarly, how the hard-headed Bernice ever got involved with a controlling charlatan like the Rev. Tauke and his band of self-righteous sycophants is anybody's guess. It just doesn't add up — and, at this length, it really should.

Finally, there's a difficulty in Rabe's inability or unwillingness to settle on a particular mode of formal exposition. Minor characters walk on and off stage to engage Janet and/or Bernice in the kind of crisply witty repartee that would make for an excellent play. In other moments, there are interludes of novelistic description. Certain scenes, particularly Bernice's ultimate exchange with Tauke and her fellow congregants, seem ripped from a screen treatment.

Ultimately, it's all a bit of a mess, which is too bad, because in the moments when "Dinosaurs on the Roof" succeeds, it is very good, indeed. It's disappointing those moments are so few.