This book was an absolute joy. Rocky might be my favorite little critter I’ve ever gotten to know through a SF novel. 

When it looks like life on Earth is doomed, a high school science teacher happens to end up on an interstellar mission to rescue the planet. His memories come back in fits and starts after years of being in a coma during the flight, but the real joy is Rocky and his people, the Eridians. Rocky is an engineering genius and the friendship between him and Dr. Grace is one for the ages. Laugh out loud funny, a great tale of interspecies learning, dialogue, translation, and friendship.