Endless Summer, Book 1

Endless Summnd in Chapter 6 (after failing to gain access to the computer), Chapter 10, and Chapter 11.
 * This book appears to have a pattern when it comes to chapter names. They appear to be named after direct quotes from that chapter. For example, the title of Chapter 5 - It's What You're Meant For - is said by Estela towards Your Character when the latter tells the former that they either want to help the former in her mission, or that they will find out what she's doing, and she simply commands them to "go back to [their] cushy college life".
 * On Thursday December 7, 2017 Pixelberry released the soundtracks for the series.
 * The old note clue is expanded further when the gang end up at Neptune Cave in Endless Summer, Book 3 trying to find the other half of island's heart.

Soundtracks
Other soundtracks can be found here.