You have to suspend a lot of disbelief to get through Bonnie Marson's novel, but once you do, this fantasy about the spirit of Franz Schubert (who died in Vienna in 1828) invading the body of a 21st-century lawyer can be fun, especially for the music lover who knows even a little about the composer and his works.

	"SLEEPING WITH SCHUBERT" By Bonnie Marson Random House ($21.95)

Moreover, this visitor won't be going away very soon: Sony Classical, which features prominently in the story, has already released a CD of Schubert hits described in the novel, and Paramount Pictures has acquired film rights.

Lisa Durbin, visiting her parents in Southern California, is in Nordstrom's shoe department when she suddenly feels an uncontrollable urge to sit down at a nearby baby grand piano and play a virtuoso sonata she does not recognize.

Since Liza has had only a few childhood piano lessons, she knows something is amiss, even if her mother insists that such talent is to be expected from her darling daughter.

Schubert, who is as confused at first as Liza about this phenomenon, communicates with her nonverbally (after all, he never learned English and she doesn't know German), and the two bond.

Schubert not only plays his music through her fingers (she rents a piano for him and keeps it in the home of a friend) but also composes new music and eventually rediscovers the lost conclusion to his "Unfinished" symphony.

Liza, her family, friends and the public greet the strange happenings at first with disbelief, then wonder, and finally acceptance of the supernatural.

Least willing to make concessions -- and last to be told the whole truth -- is Liza's fiance, Patrick Florio, who must make an important decision about taking a new position in Italy on short notice.

From the start, there are people in and out of the music business who try to exploit her, but Liza inevitably comes out on top.

The musical references will tax no one's intellect. This is a cheery, gently comic fantasy with only a few dark moments laced through.

Even when Schubert ultimately leaves Liza's body -- dying for a second time -- the prognosis for both protagonists is unfailingly optimistic.

Marson is careful not to dwell on the bleaker side of Schubert's life and music, and she also avoids questions posed by some revisionist biographers as to whether the composer was gay.

When Liza engages in some untitillating sex, Schubert's spirit inside her chastely goes to sleep. So might the reader, in fact.

If a movie version does materialize, it will be at most a mild PG.