Most descriptions I've read really lean into the physical agony. Bones cracking and reshaping is practically mandatory, you can almost hear the sickening crunch. It's never a clean, magical poof—it's messy, painful, and often humiliating for the character.
Some authors go the visceral horror route, with skin stretching and tearing, muscles knotting and reforming. That approach works well in darker paranormal or horror-adjacent fantasy. But I've noticed a trend in lighter shifter romance where the transformation is smoother, almost sensual, framed as a surge of power rather than pure torture. It depends entirely on the subgenre's tone.
The sensory details make it or break it. The smell of ozone or wet earth, the overwhelming flood of new scents and sounds as the wolf's senses take over. That's what sells the experience beyond just a visual change. A really good one makes you feel the loss of human thought, the animal instincts rushing in to fill the void.
My personal favorite depiction might be in Patricia Briggs' 'Moon Called' series. The transformation is treated as a natural, if difficult, process, with Mercy observing it from the outside. It feels grounded, which is a nice change from the constant cinematic dramatics.