I suck at eyeballing things and I suck at it in the worst way: my memory of the size of things is always smaller than the reality, so when my husband hears me say "Oh, that'll fit in our living room easy!" we both know it's not going to end well. Luckily he's quite good at eyeballing things so we don't have a 6 foot couch in a 5 foot space.
This is the reason why I grabbed this book from a closing down sale; I like comparisons; I find them much more relevant to my mind than actually measurements.
The book succeeds at its goal: it creates a standard of comparative measurements for objects of all shapes and sizes in every part of life. The illustrations are excellent and the writing is fun. My only complaint and the reason for the 3 stars instead of a higher rating is that the author tries to codify these representational measurements. For example, he calls the length of your arms spanned wide open a Len (in homage to Da Vinci's Proportions of Man). This is fine, and it works, but only when he remembers to actually tell you what his made up measurement means. I often found myself reading about something being 2 MEiff long without having any idea what an MEiff is (short for Monsieur Eiffel - the height of the man who designed the Eiffel tower) because it was described after it was used.
All in all, a fun reference to have when kids are around, but not particularly practical in its usefulness.