Here are my favorite Crichton novels, followed by some short comments
1. Jurassic Park--extensive but not intrusive info on the dinosaurs' biology and biochemistry, great action scenes with thrilling violence, compelling characters, gripping plot
2. Sphere--great overall concept, haunting imagery at several points, compelling characters (again), fast-paced and exciting plot, many memorable moments
3. Timeline--very good attention to historical detail, engrossing plot--including twists and various characters' schemings, compelling character relationships (not so much the characters themselves this time around), neato technology, intriguing mystery surrounding the identity of the traitor
And overall, I like Crichton's writing style, though at times it can seem generic. But I'm always impressed by his imagination, which seems to know no bounds given that each of his novels (except for The Lost World) explores different subject matter, though he often revisits the same themes--dangerous technology, greedy humans, a race against time, destructive psychoses, etc.