Dawn of Magic. Worldweavers, #4

Back to the Beginning With Thea Winthrop finally taking her rightful place in her society - even if she is the youngest student at the prestigious Amford University and feeling very out of her depth - something once again needs her unique talents to be set right. It begins with small things, easily dismissed, but it quickly becomes apparent that it is the biggest imaginable calamity of all. The very core of human magic has been stolen...
and it is up to Thea, the wizard Nikola Tesla, and Corey the Trickster to retrieve the heart and soul of human magic from those who have taken it... and answer many of the mysteries of Thea's life in the process. The triumphant conclusion to the Worldweavers series.