I get why this question can feel a bit fuzzy — the words 'summoning' and 'summoner' show up in lots of books and games. If you mean the YA novel 'The Summoning' that most people talk about, that one was written by Kelley Armstrong and it kicks off her 'Darkness Rising' trilogy. It’s a supernatural YA story with a haunted-house vibe and teenage psychic shenanigans; Armstrong later kept exploring similar supernatural beats across her wider bibliography, but 'The Summoning' itself is firmly her work.
If, instead, you were thinking of the fantasy YA series often called 'The Summoner' by readers, that’s the one by Taran Matharu. His franchise (which begins with the book published as 'The Novice' in some regions) grew into a multi-book arc and he also expanded the universe with companion material and shorter pieces that act like spin-offs and worldbuilding extras. So, depending on which title you’d actually seen on the spine, your author is likely Kelley Armstrong or Taran Matharu — two different flavors of summoning stories.
And for the gamers in the room: if your question is about the long-running tactical RPG franchise that’s all about calling creatures — the 'Summon Night' family — that was created by Flight-Plan and published by Banpresto, and it spawned a bunch of spin-offs like the 'Swordcraft Story' games and other handheld entries. I love how one simple word leads to such different worlds, and I always enjoy rediscovering which 'summoning' someone means when we dig into these series.