This means only client process must be able to write to the table, but all processes must have read access.

The lack of a "the" before "client" sounds incorrect. Also, which client are we talking about here? I thought only EtsPageCache was supposed to have write access to the newly created protected-access ETS table?

Therefore, I would replace the word "client" with "the EtsPageCache" in the quoted sentence above.
The OTP itself the following folder convention:

It sounds incorrect. There should be a verb after the word "itself".
It should be "operation".
At the top of page 165 of the printed book, a pluralization is missing:

one of its most important parts:
At the top of page 54 in the printed book, maps are described as:

small, fix-sized structures

Shouldn't they be "fixed-size structures" instead of "fix-sized" ones?
On page 153 of the printed book, there are two iex results shown, confusingly, in response to a single iex command:

TodoList.entries(todo_list, {2013, 12, 19})

I'm assuming that the latter response is the correct one, since it reflects the most recent version of TodoList developed in the book up to this point.

Also, there is a minor instance of excess indentation on the first "%{date: ..." line in the first iex command on the page.
In section 3.4.3 on page 90 of the print version of the book, a closing parenthesis is missing:

The function Enum.each/2 takes an enumerable (in this case, a list)