J.K. Rowling has stated that the seven books she wrote are the complete story of Harry Potter. While there may be spin-offs or other works set in the Harry Potter universe, the main series is finished.
However, we can analyze Snape's character from the existing books:
* Snape is complex and multifaceted: He's shown to be cruel and vindictive towards Harry and other students, but also fiercely loyal to Dumbledore and deeply protective of Harry's mother's memory.
* His motivations are driven by love and loss: His actions are largely shaped by his past love for Lily Potter and his hatred for her murderer, Voldemort.
* He is ultimately a hero: Despite his flaws, Snape ultimately sacrifices himself to save Harry and defeat Voldemort.
Whether you consider Snape "evil" or not depends on your interpretation of his actions and motivations. But it's clear that he is a complex character with a tragic backstory and a pivotal role in the Harry Potter story.