Here are two passages on the subject from The Divine Conspiracy:

I know that, as far as forgiveness alone is concerned, the tenderness of God is far greater than we will ever understand on earth or perhaps elsewhere. That is surely what it means to say that he gave his unique Son to die on our behalf. I am thoroughly convinced that God will let everyone into heaven who, in his considered opinion, can stand it. But “standing it” may prove to be a more difficult matter than those who take their view of heaven from popular movies or popular preaching may think. The fires in heaven may be hotter than those in the other place.

It might prove helpful to think occasionally of how, exactly, I would be glad to be in heaven should I “make it.” Will it be like a nice, air-conditioned luxury hotel with unlimited room service and spectacular amenities for eternity? I often wonder how happy and useful some of the fearful, bitter, lust-ridden, hate-filled Christians I have seen involved in church or family or neighborhood or political battles would be if they were forced to live forever in the unrestrained fullness of the reality of God…and with multitudes of beings really like him. (pages 301-302)

Perhaps, by contrast, we must say that those who do not now enter the eternal life of God through confidence in Jesus will experience separation, isolation, and the end of their hopes. Perhaps this will be permitted in their case because they have chosen to be God themselves, to be their own ultimate point of reference. God permits it, but that posture obviously can only be sustained at a distance from God. The fires of heaven, we might suspect, are hotter than the fires of hell. Still, there is room in the universe for them. (page 398)