To make a very long story short yes, put your 18 month old down to sleep and let him sleep. If he has an actual need then tend to it but if he is just protesting because he doesn't want to sleep or is relying on you to soothe him, then let him CIO.
I have the book and I love it. If you read more deeply into the book, you'll learn a whole lot about sleep cycles, circadian rhythms, how much sleep hygiene children need, how sleep debt affects so many aspects of life, etc. You will NOT find a checklist of multiple steps to follow.
Your child will not be emotionally damaged by this - just ask my 4 year old! As a mother (unless there is an emergency) you know that your child does not NEED to be awake in the middle of the night, likely does not NEED to be fed, and does not NEED to be up and playing. What he NEEDS is to get a nice solid block of sleep for several hours overnight so his gets proper growth and development. He is demonstrating a WANT to you and you have to pick your battles and decide how you want to approach it. CIO will be the quickest and easiest way to get your child sleeping again. I completely trust Dr. Weissbluth as he is a pediatrician who specializes in infant/child sleep issues with over 30 years of actual research and tens of thousands of infants and children as opposed to someone who just prostletyzes over sleep because they have an MD and/or are interested. He is still practicing in the Chicago area.
CIO is usually more difficult for the parent than it is the child and you are the only one who has to walk in your shoes and deal with your situation. No matter what you choose, be consistent with whatever you decide so that your child gets ONE message as to what you will be doing regarding the sleep.
Good luck - for what it is worth, I used Weissbluth's techniques with both of my kids. They were consistently sleeping through the night from 6 months on, nap great, and get an appropriate amount of uninterrupted sleep each night. CIO took literally 3 days with my older son and 2 days with my younger son (at 6 months of age).