Quick-take: Very long wind-up.
Kevin suffers from a rare serious illness. He has roughly 6 months to live. One of the side effects is hallucinations, or so it seems. These visions are oddly specific. When investigated further, could it be messages from aliens. A quick drive over to SETI, and the book enters its main plot.
This book annoyed me so much. The "science" is trash. These researchers sure seem quick to agree with whatever a 13 year-old boy tells them to do. The book handled that by having Kevin make some very timely predictions. I could accept that except the messages themselves are also terrible. It is all tropey generic "we come in peace" type messages. There is absolutely no meat to it. A 13 year-old boy truly could make that stuff up on the fly.
I don't like revealing too much plot in these summaries, but there is another piece that is very frustrating. One of the messages is corrdinates to find an object, which they do find. There is so much absurditity though... 1. Those corrdinates conveniently work within whatever mapping system we have versus the aliens. 2. The physical object is available to be found on Earth near the surface despite light alone requiring 40 years to get here. 3. All these messages are so timely as the plot moves along. 4. All these astronomical events can happen within a few months before the boy's illness becomes unbearable.
Those are just the planet-sized holes I could think of as the plot moves. Sci-fi should have at least some grounding in actual science. Otherwise, just go full-blown fantasy and reign it in with a rules system.
Score 3/5. 90% of the book is searching for aliens. The cliff-hanger makes book 2 feel quite different, so I am giving it a chance.