I've read almost all of Murakami's books, and I would rate this one somewhere around the middle. It was good, Murakami's trademark surreal-storytelling-that-doesn't-make-sense-but-also-does-make-sense is on display here, and the way the story converges ends the book on a high note. Hard-Boiled Wonderland is probably the most sci-fi of all of his I've read. The setting is cyberpunk lite; featuring warring factions of data calculators and a scientist who implants circuits into brains. On the other side, there is a parallel story set in a fantasy world of golden beasts and dream reading. It's all very Murakami.
One thing I love about Murakami's stories is that they almost seem to transcend a desire to decode their meaning. Oftentimes when people talk about books, they discuss what themes were present and what the symbolism represents. With Murakami, I never feel that need. I accept the stories at face value and enjoy getting lost in a world, similar to how the narrators are generally taking everything that comes at them. It's as though the sense of discovery that comes along with reading the book is the meaning of the book.
The reason I put this one towards the middle of his books is that the bridging of the gap between the worlds didn't feel as strong in this one. There's a much stronger sense of this in Kafka on the Shore, where the protagonist slips between two worlds seamlessly and often without his own knowing. In Hard-Boiled Wonderland, the two worlds are there but they never really... click together. I don't know, it's kind of like there is this second world and it is explained why it exists but the lack of overlap between the two is a bit of a miss for me. I think one of Murakami's strongest suits is the ability to connect seemingly unconnected worlds in a fascinating way, but it never really comes together here. Sure, we learn why the other world exists, but it's just kind of there. It's missing the trademark linking that always brings out the best in his stories.
Overall, the book is an intriguing exploration of the mind but it's not his strongest outing. I would have loved to have seen more connection between the world (I guess the title really was telling me there was a separation) and I would have liked a little more background on the world. The setting was interesting but was hardly fleshed out, and I would have loved a bit of Murakami mythology sprinkled in there. I enjoyed the book quite a bit, but a lot of it was carried by Murakami's smooth and simple prose.