The benefits of going into a book completely, of being completely absorbed by it:
…you absorb everything in the authors mind, their way of life, patterns of thinking (how they arrive to certain conclusions, their mental shortcuts, etc.) character, outlook, disposition, mental modes/frameworks… That is to say, reading in this way gives you a new lens with which to view the world. It can help you to open your eyes and experience new/alternate patterns of thinking that might not have been possible before. This is obviously a good thing, and mainly for some of the following reasons: 1) you gain more clarity about the world 2) you are better able to express yourself 3) with more knowledge, insight, and wisdom, you can create new ideas and/or inventions 4) you can better help others 5) you can better understand your enemies (keep your friends close and your enemies closer [to paraphrase Sun Tzu]).
Sometimes however, when reading this way, facets of the author or his/her writing may not resonate well with you, and this can be tough. It can be hard to push through. But… if this does occurs, the benefits of you pushing through are that your overall character is strengthened. And when you do get through, you’ll have gained these new mental models while at the same time gaining the refreshing clarity that YOU ARE NOT THEM. It’s sort of the same feeling you would get when waking up from a semi-uncomfortable dream to find out that it wasn’t real…
…and this leads to the first potential downside to exhaustive reading/book analysis: if you have a weak disposition, you may begin to take the shape of the author when you really should just be being yourself. However, another downside (and arguably more important because it is so subtle) is that, since time is the only true scarce resource, you may be wasting your time performing useless analysis when you should be doing other things (i.e., the opportunity cost is very high).
So, is it really worth your time to read this book thoroughly, absorbing every detail, every argument, thinking about the arguments/facts in ever so many different contexts? You have to do a cost benefit analysis, weighing the benefits against the costs. Which is more beneficial to you? Absorb the book completely (in the case that you need to gain more perspective on life, more lenses, more ways of viewing the world)? Or take only what you need and get on with your life? There is a time and a place for both.