Corruption (Grumpy Old Wizards Book 2) by John O'Riley

In this contemporary fantasy, we continue the adventures of Josephine O’Connor, a recently retired grandmother who has always enjoyed a youthful body due to extremely slow aging but when she discovers she’s become immortal, she must return to the workforce and leave retirement behind for good. Soon after starting her investigative work for the police, Josephine finds herself smack dab in the middle of trouble when she discovers a secret organization called the Valituras that has amassed ancient magic and power with single-minded determination. To further complicate matters, her grandson’s new eighteen-year-old friend starts flirting with her like crazy but when she gives him a pity date, her intuition tells her there is far more to him than meets the eye.

Josephine realizes she may be in over her head when the Valituras ramp up their attacks and end up casting an immortality curse on her best friend, Helen, by mistake. Fortunately, Helen isn’t too broken up by the curse. Who wouldn’t want to live forever in a young, perfect body?

Of course, everyone knows that dark magic always comes at a cost. Can Josephine safeguard her loved ones while defeating the Valituras before they achieve their nefarious goals?