How well does the textbook you use in your course fit? What I mean by that is:
- Have you looked at whether the reading style is geared toward the students you typically encounter? Is the text written for beginners or experts?
- Have you compared your actual expectations (objectives & expected outcomes) to the content available in the textbook?
- Is the textbook organized in way that facilitates learning by both reading and raiding?
Of course, no textbook is going to fit you, your students, and your course like a glove. Even if you create your own, or edit a custom version of existing text material, the fit will change as you and your course evolves as you gain teaching skills, adjust your techniques, and your students' needs change.
Textbooks fit like a mitten, not a glove. Because the best they can do is approximately fit course objectives and content, student learning needs, and your teaching approach.
But mittens are great. They cover your hand and give you some wiggle room.
As a "mitten" your course textbook should cover what you need it to cover. It's okay if it covers a bit more than you need. That extra coverage will used later for reference and future learning in professional and clinical courses. Extra content also helps fill in prior learning gaps, which allows students to "get it" on their own as they read or raid. And extra content may help students better see the context and importance of the required content. Satisfying natural curiosity is not a bad thing, either.
Although well-fitting mittens cover a bit more than they need to, a mitten should not be too big. So having so much content in a textbook that it's hard to stay focused mainly on the required content is not good for learning. Conversely, a mitten should not be so small that you can't get it around your big hand or wiggle your fingers a bit.
Some mittens have special features like a slit through which you can extend your fingers when you need more precise movements than your mitten will allow—as when opening your flask of hot tea. If your students would benefit from a supplemental atlas, an audio glossary, a list of word parts for each term, or other special learning features of textbooks, then consider those carefully, too.
The key is to think of a textbook as an off-the-shelf item that will never fit precisely. It's up to you to make sure it fits well enough. And the only way to get that fit is to try on all the mittens. Don't just glance at them, really put your hand in and see what they're like.
Plaid mittens are the best. That has nothing to do with the analogy I'm making here—I just like plaid mittens.