Level II of the CFA exam is considered the most difficult of the three. In general, I did not find the material more complex but it did delve deeper into core concepts compared to Level I. The reason that level II is the most difficult is a function of both the material and the level of competition. All the candidates that take level II are obviously diligent, intelligent and understand the test conditions. So this time around you're studying against peers who didn't just sign up on a whim or cajoled by their firm.
The CFA institute now issues course materials along with optional sample exams. I still bought Schewser notes and I regretted it. If you are a disciplined individual who can self-study, I highly recommend just using the materials that the CFA insitute sends. The books and sample exams are great.
I studied from the beginning of February to June. At the time, I was working about 70 hours a week. When I wasn't working I was studying. If you're serious about passing this exam, I recommend you do the same.