A lot of library instruction books I've read tend to cover only one aspect of instruction, are too heavily rooted in theory (or the other extreme, are practical only), and often are not very customizable. What I especially liked about RTEL was that it had an even balance of theory and praxis, was able to be customized for academic instruction librarians and trainers (with some applicability for other librarians as well), and also had a personal voice. It's not too often that authors will talk about personal struggles getting accustomed to doing instruction, so it was really nice to hear that someone as capable and skilled as Char Booth was actually nervous at some point and was able to grow into the skillset she has now. Knowing how to teach is not really an innate quality in most people.
The book introduces theory, gives practical examples, and offers opportunities for reflection in worksheet-style questions and summary questions after each chapter. Different aspects of instruction (information technology, educational theory, and instructional design, for example) are drawn upon throughout the book through Char Booth's USER method: Understand, Structure, Engage, Reflect. It's also holistic in covering developing lesson plans, differentiating instruction to reach multiple learning styles in student-centered instruction, and the very important assessment.
A common theme throughout the book is to consider WIIFM, or "What's in it for me," that students either actively or subconsciously wonder, and this is an important key to get and maintain interest, as well as direct instruction.
Analyzing students through this principle as well as some suggested learner analysis strategies helps to paint a better picture of how to develop instruction and related materials. This more naturally leads to better assessment, and for those confused on the distinction between objectives and outcomes, these are delineated with real-life examples given for each. To clarify, according to the book, objectives are, "...learner-focused, action-oriented statements that provide the concrete criteria to evaluate if learning has occurred." Objectives are linked to Bloom's Taxonomy, and examples are structured as a condition, one or more actions, and a performance standard. An example given in the book is: "Given access to bSpace and a computer, the faculty member will be able to upload ADA-accessible files to the Resources are a of a course site. (taxonomy level: Understanding, Applying)."
Outcomes, on the other hand, are "the actionable, real-world result of the interaction..." A related outcome provided as an example is, "Faculty will provide more online course material through open access and library subscriptions."
There is so much more great information in this book I'd love to highlight, but I'm going to cut it off here; as you can see from these examples, material is explained in an easy-to-understand way that is still intelligent and thought provoking... just how instruction should be.