First, a few warnings: this book has no female lead, does not break up the canon couples, and does not involve transmigration. It adds an original story to the canon, though you can enjoy it even if you haven’t read the original.
“Happy birthday, Brian! Today is your eleventh birthday. Open the present Mom prepared for you!”
A gift box carefully wrapped in colorful ribbons shimmered with flecks of gold beneath the bright lights.
“Wait, wait, Brian! Look at what Dad got for you first!”
As he spoke, he took a letter from inside his coat…
“Letter of Admission to Hogwarts.”
And a wizard hat, knitted by Mom herself.
“Our little wizard, go on, gently tear open the magic!”
Keep going, it's just a bit complicated.