l.1 The default cases uses
-->             case

FIXED

Index / Ch.15 Case Clases and Pattern Matching, p.271 [pdf 301]: 
to index entry for "`(backtick)" add "in constants, 271"

DONE

A very little mistake:
"You can use a typed pattern as a a". The 'a' is written twice

FIXED

the '@'-sign entry in the index should include variable binding as a
sub-entry

DONE

Divisions such as "x / (x + 1)"

FIXED

It states at the bottom of p280:

"The operators isInstanceOf and asInstanceOf are treated as predefined
methods of class Any..."

Looking at the ScalDoc I see that isInstanceOf and asInstanceOf ARE
methods of Any.

Thus, I would rewrite the above as:

"The operators isInstanceOf and asInstanceOf are predefined methods of
class Any..."

The use of "treated" suggests alias/synonym.

At the bottom:

case s: String if s(0) == 'a' => ...

will throw a StringIndexOutOfBoundsException if s == ""