In this 700-page book, Todd Tomasella carefully explains his position that "once saved, always saved" is false by using the authority of the Bible. He does so with a humble heart and comes across as someone that is doing so because he deeply cares for those that could be misled about the concept that the grace of God somehow gives us a license to sin and that there are no consequences.
Todd is careful to defend those that speak out against it and is not claiming that works, or being perfect, or anything short of the sacrifice Christ made on the cross is the way to heaven. He points out that we must have that first and foremost, but then scripture explains we should not willfully and continually sin.
An increase in apostasy is foretold to happen in 2 Timothy 4:3-4: "For the time will come when men will not put up with sound doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear. They will turn their ears away from the truth and turn aside to myths." I believe Todd does a great job of digging into what is likely one of the biggest, yet most subtle, apostate doctrines being taught and accepted today (and because it appeals to "itching ears", it is very widespread and deeply rooted in Christian circles that otherwise have very sound doctrine).
I highly recommend this book to anyone that wants to do more research on the topic, as it is a great resource for doing so.