The Spurs manager has compared the German international to former White Hart Lane favorite Rafael van der Vaart and has praised his versatility.
Spurs completed a deal for the midfielder on Monday for a fee of 1.75 million euros and the Portuguese manager is delighted with what he thinks is a wonderful piece of business.
"Is he the bargain of the century? I think so because it's difficult to find a young player who is running his contract down and we faced tough competition," Villas-Boas said in the Daily Star. "He's recognized as an exceptional young talent and we have high expectations of the player."
He added, "Because of his creativity you can compare him to Rafa [van der Vaart] - to a certain extent anyway because Rafa was a greatly experienced player when he joined and Lewis has all his career ahead of him.
"He will fill the No.10 position, although he can play on the right or the left and he has also played in a holding role."
Holtby could make his competitive debut for Spurs as they travel to Norwich on Wednesday night, and Villas-Boas says he could tempted to throw his new man straight into the action to bolster his attacking options.
"He's been selected. Is he ready to go straight in? It depends, but his English background can help him and he knows the culture and the language very well," he said.