This passage is an incredible promise: not only does it say that unbelievers who read the book of John, if they are the sheep of John 10, will see Jesus as the Messiah and be drawn to Him, but it also promises that those who have already been born again and read it will be kept. Get up in the morning and read this book, and God will keep you a believer.
Today I am finishing my 5 month study on the Gospel of John, and have I found that to be true! John 1:14,16 says that the Word became flesh and dwelt among us, and we beheld His glory, glory as of the only begotten of the Father, full of grace and truth… and from that fullness we have all received grace upon grace. By beholding Him in this gospel I have received much grace.