The book currently uses $X \amalg Y$ notation for binary sums (coproducts) in Chapter 2 (An introduction to univalent mathematics). However, in Chapter 3, Section 3.3 (Set bundles) an example uses $S^1 + S^1$ notation although up to this point $+$ has only been used for addition of numbers.

I am not certain if $S^1 + S^1$ should be changed to $S^1 \amalg S^1$ or an explanation of this syntax is due.