Best Web Application Security Resources

I am a full Stack Web developer, and i develop all purpose sites . I am always worried about my Website Users Data whih is stored in Database. what I want to know is , Is there any way I can achieve if not 100% , atleast 80% assurance that my Data is Secure and hacker proof to a great extent. I am mainly in search for a small book which I can refer and am not much into Security for Web . I just need a simple solution to ensure data protection.

Thank you