Extremely easy professor, and this is coming from a dumb guy. If you attend lecture, you'll know what you need for the exams. The book reading will only be over what was emphasized in lecture, which he makes fairly clear. The exams curves were generous. On the first, a 17/25 was an A-. On the second, an A- was a 19/25. The final was obviously more difficult, but FAIR. He even recycled a few old questions from the previous exams. But be careful -- professor Bern can be a tricky fellow: make sure to read the questions CAREFULLY. Bern also likes demonstrations. Most of the time they didn't work, but they're still helpful (when they work). Overall, Bern is a good professor. Highly recommended.
Professor Bern explains the material very well. He is also very reasonable about workload and exam difficulty. The final was incredibly hard but however that was compensated by his grading policy. His class is overall rather difficult but that was only because complex variable theory is difficult.