This book wasn't quite what I was expecting. Reading the subtitle and blurb, I was expecting a book about developmental biology, with some discussion of how its particular theories were developed and used by biologists. What I got was a book about the philosophy of science, in particular, the different role of "theory", "mathematical model", and "experiment" in physics and biology, illustrated by examples from the history of developmental biology. Never mind: it's a fascinating, and eye-opening, read.
The main thrust of Keller's argument (or at least, the aspect I picked up, as a physicist-turned-computer scientist now working with biologists) is the major difference in starting point in the physical and life sciences. Summarising brutally: physicists start with theories and models as central, and use these to suggest experiments, and use experiments to refute (if one is being a good Popperian) the theories. Biologists, on the other hand, have the observations and experimental data as central. They then, maybe, sometimes, build models of the data. But any such models are incredibly detailed, incredibly specific to particular systems, with very little, or no, generality; there is no, there can be no, abstraction to the kind of general theories that are the life-blood of physicists. Biological systems are just really really complicated, and abstractions lose too much of what's important. Hence biologists have little or no time for (necessarily abstract) mathematical models or general theories.
For me (ex-physicist and all), this isn't "Making Sense of Life": it is "Making Sense of Biologists". And that is also interesting.