Some things are yours, and they will always be yours; what is not yours can never be forced without ending in illusion.
That vial of Harry's blood was something Ye Feng had specifically prepared for Voldemort Two, while the book was meant for Lucius. Ye Feng feared that Lucius might not dare to bring Voldemort Two back, or that even if he did, Voldemort One would snuff him out before he could grow in power.
Although having this Secret Manual did not guarantee Lucius would be able to master it, and mastering it did not necessarily mean he would surpass Voldemort, it was still better than nothing. That was why Ye Feng gave Lucius a little reward.
Chapter 296