Anyone who has raised a child understands the difference between relationship and fellowship. A parent has a permanent relationship with his/her child. But fellowship is a different matter. To have fellowship with a child means the parent and the child are enjoying their relationship; and though their relationship is eternal, their fellowship is not.
The Apostle John wrote one book about how to have an eternal relationship with God--the Gospel of John (John 20:31). And he wrote another book about how to enjoy that relationship by having fellowship with God--First John (1 John 1:3-4). Dr. Anderson explains that First John is not about whether one has an eternal relationship with God, but it is about how to enjoy that relationship by having fellowship with God.
Dr. Anderson has done a great job fending off the incorrect interpretation (in my opinion) that teaches 1 John as a book about tests of salvation. He made clear that it stems from Calvinism and reformed theology.
However, though I would agree with his theological paradigm, he argues about it to a fault, where he sometimes rambles about it. I wish his book was more expositional than devotional, going verse by verse.
Though these issues are in his book, I would recommend it for any student of the Bible. I know very few commentaries on 1 John, and I know even fewer commentaries of the epistle with a non-Calvinistic interpretation. This is a good place to see the epistle as one about fellowship.
First John is written to Christians to encourage us to abide in Christ. It's written about our condition, not our position. The author says that the key verse of 1 John is not 5:13 as many teach and believe, but 1:3-4.
This book is a breath of fresh air in helping Christians to live as God intended. It is an excellent commentary on our fellowship with God.