It's not uncommon to get a few negative comments for even the best instructors.  Some of the comments I've gotten have been so bizarre that it made me wonder about the sanity of those students.  

One student, in particular, went on a 3 paragraph rant about how it offended him that I used a Barbie car to demonstrate inertia for my physics class.  (I tend to use a lot of toys.)

In another case, I got one very negative evaluation and in the comments the student said that I wasn't good at teaching C++.  Since I teach physics and not programming, this was more than a little strange.

So don't sweat it.  

If you want to take the feedback seriously, one thing you can try is running a problem from the chapter for each class.  This can hook in the use of the book, and give the students some traction when running the rest of the problems.  This is something to try anyway.

Additional:
One of the tricky things is to bridge the gap between 'how' and 'why'. Some lecture instructors will only explain the overarching concept (the 'why') and leave the detail work of running the problems for the students to figure out (the 'how'). But this often leads to a disconnect, so the students will spend a lot of time spinning their wheels, trying to see what the lecture has to do with the actual problem sets that they are asked to work.

With physics and math (the topics I typically teach) it's possible to construct problem sets for most topics that include the 'why' in the 'how'. That is, the procedure for doing the problem involves a conceptual approach to problem solving. Making a connection between the big concepts that we talk about in lecture and the problem solving strategies that the students have to develop for their homework sets is key