T.A. Barron mixes spirituality, physics and ecology in his debut novel, and the result is a thoughtful and appealing book.

Kate's favorite after-school pastime is to visit her grandfather, a renowned astronomer. Quiet and introspective, she finds her grandfather's company preferable to that of her peers. Often, she spends her visits browsing his library, daydreaming and reading while he works in his lab.

Lately, though, Grandfather has kept himself shut up in the laboratory, working such long hours that Kate scarcely gets to see him at all. One day, she lures him out for a picnic and learns that his work concerns faster-than-light travel, and somehow, it has something to do with a beautiful blue butterfly called a morpho.

Grandfather shuts himself back into the laboratory after the picnic, but Kate, sensing a strange and dreadful presence, barges into the lab. Since she is curious about his work, he reveals his discovery: pure condensed light, the secret to faster-than-light travel. The key is that pure condensed light, or PCL, interacts with humans in a way that releases their heartlight -- the human soul. In the form of heartlight, an individual can travel anywhere in the universe.

The focus of Grandfather's studies has been a star, Trethoniel, which should have collapsed into a black hole, but which reversed itself. It appears to be manufacturing its own PCL, and Grandfather's work revolves around discovering this process. But he has made another discovery: that Earth's sun is rapidly losing PCL, and unless this stops, the sun -- and Earth -- have only two or three years left.

When the presence Kate felt turns out to be a kind of ghost bent on destroying the lab and stealing Grandfather's work, the astronomer takes action. He has manufactured PCL and built a special ring to hold a small quantity of it -- a band with a butterfly on it. He fills the ring and vanishes, despite Kate's protests. All she can think to do is find the ring he made for her, fill it, and go after him, and thus the adventure begins.

Kate encounters a thing called the Darkness, a corrosive dark cloud which attacks her. She falls into a snow-covered world and is rescued by creatures who look like snow and ice crystals. The snow crystal, Ariella, befriends her in her search for Grandfather, answers, and the ring which has fallen off her finger and without which she cannot get home.

The planet is in trouble. There have been changes in the atmosphere which are damaging it, and the crystal people who live on the planet have been struggling a long time. Kate and Grandfather must fight the evil which threatens not only the planet but the universe, and most important, must be able to identify it.

There is a strong spiritual element throughout the book, which is very reminiscent of the works of Madeleine L'Engle. Grandfather talks about a Pattern, about how everything that happens is part of a grand design, and he and Kate sing her bedtime prayer, the "Tallis Canon," which becomes integral to the story and is often a motif in L'Engle's books as well. Grandfather's character is fascinating in that he represents a man of both science and faith. Kate proves herself to be strong, resourceful and determined; her growth through the novel is subtle and believable. Her self-confidence is hard-won and genuine.

The story itself is fast-paced and compelling, pulling the reader right into the pages, and while the writing is occasionally awkward-sounding, it does not falter more than most first novels. Barron doesn't make his messages too obvious; there is emphasis, but he does not bludgeon the reader. The debt to L'Engle is apparent throughout but, overall, Heartlight will definitely appeal to L'Engle fans.