John le Carré makes smooth writing look easy. It's not needlessly florid, nor is it noticeably sparse and hardboiled. It it very Smiley-like: unassuming but effective. 

As others have said, this isn't a spy novel, it's a mystery George Smiley happens to be in. But a good mystery! 

I enjoyed a nice meander through class politics and academic culture alongside the murder mystery. My only gripe is that the ending wrapped up a bit too quickly. All the build up was great, and then a three page "so here's what actually happened" speech and it was over. 

Excited to plough ahead to the actual spy novels!