With permission of the DM you are allowed to select 3 spells of your choice.

To add a spell or cantrip scroll to this book, It will take a long rest to transcribe a cantrip, in order to transcribe a spell it will be 30 days per spellcasting level <may store up to 9th level spells, each spell will have 3 spell slots. all slots will recharge after a long rest> 

 This Feat gives you a max of 25 spells.