I'm sorry you're not enjoying the book hench but by no means are you being a killjoy ... as Pam has said that's why we read it as a group.
This book is a bit more academic than some we have looked at in the past, so don't worry about that just try and remember that the academic parts are mainly explanations about 'where' some of the ideas we have 'grown up with' have come from in the past and these were all ideas that older civilisations than us had about heaven - not the definative answer to 'what, why, how and where' heaven is.
The part about heaven not being permanent comes on page 10 (we did not have enough time to get to that more fully)
The author, I believe is saying that in the New testament particularly there is talk of 'heaven and earth' passing away so heaven cannot be seen to be everlasting ... it will pass away like the earth at the end of all times.
It is assumed that this is the heaven as refered to in 'the sky' rather than God's dwelling place and so it is the sky that will be renewed with the earth.
But because 'heaven' is refered to as in the sky and as in God's dwelling place the word seems to be used 'interchangeably' for both and this is a bit confusing.
''Heaven, therefore, is not in and of itself everlasting. The term everlasting is associated
- with God: from everlasting to everlasting you are God' (psalm 90)
- with God's characteristics: 'O give thanks to the Lord, for he is good; for his steadfast love endures forever' (1Chronicles 16)
- and God's word: the grass withers, the flower fades; but the word of our God will stand for ever'(Isaiah 40)
God is permanent and everlasting but heaven is not: it will pass away and be replaced by a new heaven
.'' (page 10)
we are then asked to consider that if by eternity we mean ever lasting then heaven cannot be, since it will pass away with earth. BUT if by eternity, we mean 'outside' time - especially as we know or understand time - then heaven may indeed be eternal.
She goes back to Psalm 90 which also says
''for a thousand years in your sight are like yesterday when it is past, or like a watch in the night' God's time may be very different to ours and God is eternal.
She also explores the idea that this veiw of heaven may tell us also about God's love for us ... she says
''if God created heaven and will re-create it, it must be possible for God to dwell somewhere other than heaven'' (page 10)
So maybe one purpose of heaven is to be a place close to earth - but not God's only dwelling place - for God to 'be' alongside us .... a reminder that God wants to be close to the 'realm made for that purpose'
Remember too that Jesus told us in John 14
“Do not let your hearts be troubled. You believe in God[a]; believe also in me. 2 My Father’s house has many rooms; if that were not so, would I have told you that I am going there to prepare a place for you? 3 And if I go and prepare a place for you, I will come back and take you to be with me that you also may be where I am. 4 You know the way to the place where I am going.”
Jesus then, perhaps said something about the nature of heaven as God's dewelling place I think ... 'many rooms' could also suggest that there is more to heaven than being just one kind of place above us.
I hope that helps ... I have to say my honest answer is that I do not know what heaven is, how long it might last or where it is ... I am hoping that the book will help me - and all of us - think about that and explore it