It's a tough one to recommend... I appreciate it greatly, and it has all the features of later Zachtronics games that are perfectly designed to get me hooked... but you can definitely tell this is Zachtronic's earliest release.

The actual individual puzzles ramp up very quickly in complexity and quickly become far, far too bloated and long. In later Zachtronics games such as Opus Magnum, I've always found that its relatively easy to get /a/ solution, and the fun comes from refining your solution until is perfect as can be. In SpaceChem, I just found it was a relief to be done with each one. It also ends up being pretty common to spend literal hours on a puzzle only to be scuppered by some interaction you weren't expecting right at the end, and having to start everything again from square one. It all conspires to end up being a very frustrating and poorly paced experience, and it feels unlikely I will ever get round to properly finishing it.