I would read the book regardless of whether you choose to make the move or not. It'll give you a good idea of what the day in the life of an SE is like. I found it to be accurate.
As for being afraid of giving up that hard skill:
1. Unlike going into actual sales or management, you don't give it up entirely. Your technical skills are still very valuable. It will give you confidence when you demo stuff and clout amongst engineering types (which are key to getting the technical win). It's just not THE thing that your performance is measured against.
2. Having presales experience will help you significantly if you choose to go back into full time engineering. You'll have a better idea of what customers want and how sales are made. This will help you gauge when/how to build the right thing and approach sales-y/business people.
In fact, my biggest pet peeve with engineering is that unless you're working at the earliest stages of a startup, you're so far removed from what customers actually want but are incentivized on your tech prowess. This creates perverse motives that tend to be more complex and anti-customer in the name of software craftsmanship and scalability.