THE name Alan Ayckbourn is above the title and he also directs, putting the seal of approval on this musical version of his 1998 play about a boy who finds himself inside the pages of his favourite (and some not-so-favourite) books.

Ten-year-old Kevin is an avid reader plunged into the world of his fictional hero, hard-bitten but not-as-tough-as-he-makes-out private investigator Rockfist Slim. Together they embark on a quest to defeat the Green Shark and save the world. The trouble is that If characters from other volumes on his shelves - including Kidnapped, Chess For Beginners and a book of ghost stories - appear and hold them up as the villainous Monique gets ever closer to catching them.

The story is full of fun and inventiveness reflected in Ayckbourn's direction, Michael Holt's imaginative designs and Jason Taylor's lighting.

But this is a musical so the songs need to stimulate the imagination as well and they succeed admirably. Paul James (musical adaptation and lyrics) and Cathy Shostakovich and Eric Angus (composers) - the team behind The Demon Headmaster stage musical - offer numbers that are clever and catchy. One, Kaboom Kapow, has already won an award as best new musical theatre song of the year.

As Kevin, a gender-bending Evelyn Hoskins brilliantly conveys the wide-eyed wonder and youthful spirit of a boy having the adventure of a lifetime. She's well-partnered by Nicolas Colicos as the supposedly hard-bitten private eye needs a boy to get him out of scrapes.

The rest of the small but versatile company skilfully, and often hilariously, inhabit a variety of fictional characters come to life. And The Wubblys, a detour into Teletibbies territory, are sheer delight.

  • Runs until Aug 31. Box Office: 01723-370541 and sjt.uk.com