Many fans of the series will be familiar with Buffy the Vampire Slayer. Sarah Michelle Gellar plays Buffy Summers, a Slayer chosen by fate. She is a woman with supernatural powers who is humanity's hope against the forces of evil. When a Slayer dies, a new Slayer is automatically summoned. In this case, Buffy is the chosen teenager. After setting fire to a gymnasium full of vampires, she was expelled from school. Her mother and father are divorced and at the start of the series, Buffy arrives with her mother in their new hometown of Sunnydale. She is determined to leave her destiny as a Slayer behind and live a normal teenage life. However, when she arrives at her new school, her Watcher, librarian Rupert Giles, makes it clear to her that she cannot avoid her destiny as a Slayer. A Watcher is a Slayer's guardian who watches over her, trains her and provides her with information and advice. Her destiny is to kill (mainly) vampires.
The character Angel is introduced in the first season. This character is played by David Boreanaz. I personally know David from his roles in Bones and Seal Team, but before that he emerged as the character Angel as a crowd favorite. You could write a column about it. The makers quickly realized that Angel was a beloved character among the viewers. This quickly gave rise to the idea to further explore the story of Angel in the form of a spin-off.
In 1999, during the fourth season of Buffy the Vampire Slayer, the spin-off Angel premiered. Angel, originally known as Angelus, is a vampire who is over 240 years old. He was infamous for his brutal acts and murders in Europe until he was cursed by a Romani tribe who restored his human soul to him as punishment for murdering one of their own. This curse gave Angel a conscience and filled him with guilt over his centuries of murder and torture. After returning to humanity, Angel left Sunnydale and Buffy at the end of the third season of Buffy the Vampire Slayer to move to Los Angeles in search of redemption. In Los Angeles, he works as a private investigator, helping people in need while struggling with his own demons and past.
Despite Buffy the Vampire Slayer and Angel being set in the same universe, the series do have different styles and themes. Buffy the Vampire Slayer combines horror, action, and coming-of-age elements with a lighter, humorous tone. In doing so, they deal with themes such as adolescence, identity, and the battle between good and evil, often with a metaphorical approach to the challenges of growing up. The spin-off Angel takes a darker, more mature tone. Angel focuses more on mature themes such as redemption, guilt, and the complexities of moral choices.
Both Buffy the Vampire Slayer and Angel have left a lasting impression on fans. Although Angel is a spin-off of the original series, both series have managed to create their own charm. Both series are a valuable addition to the series landscape due to their innovative approach to the horror genre. Because of this, I conclude that Angel has become a successful spin-off.
Angel was certainly not a continuation of Buffy, but a real (successful) spin-off. I could also imagine that not every Buffy fan is automatically an Angel fan, but in practice I think that turned out to be quite the case. Actually I had expected more spin-offs of the Buffy-verse, but this is all, except for an animated version. I did read that there will be another reboot.