Unfortunately for you, there isn’t an automatic different-EQ-setting-per-genre feature, and you would need to change the EQ manually.
I don’t know if you’re doing it this way, but you also can change the EQ setting by starting your audiobook or tune, clicking the down (6 o’clock position) button, and then scrolling down to the EQ option in the list–not as good for you as auto-switching, but easier than doing this otherwise.
This only works if you are playing files from the Music menu. When playing Audio Books and press the down button, this option is not available.
…Or at least… to have easy way to change equalizer settings while listening to audiobooks. Now I have to leave audiobook, play some music, change equalizer settings and return to audiobook to achieve this.
Is there a way to make it easier?
You don’t have to go through this. There’s no need to go into the Music menu and start playing a song in order to change the EQ, but since there is no EQ settings in the Audio Book menu, there are a couple of button presses you must go through.
While playing your Audio Book, press the Home button once to go to the Main Menu. Press the Up button once (assuming you land back at the Main Menu with the Music menu on the screen). One press up is the Settings Menu (once you access this menu, it will return back to it automatically when you press the Home button).
Press the center button to enter the Settings menu and then again to select the top option, Music Options. The 3rd option down is the EQ settings. Here you can change the settings to your individual preference while listening to your audio book. Once set the way you like it, just press the Home button twice to return to the Playing screen.