I clearly remember the excitement I felt in 1977 when my brother gave me a first edition hardback edition of the Silmarillion. I had just read Lord of the Rings and already had a box set of Tolkien's other writings. I launched into the Silmarillion and did not get very far. Several times I tried but it was too dense. I lent it to a friend who persisted through it over about six months admitting it was hard going.
This year after reading a biography of Tolkien I have been working my way through all his writings and I once again attempted the Silmarillion, this time in Kindle edition. I persisted and ultimately completed it. It is undeniably a classic work but more than that, if it wasn't for the Silmarillion we would have The Lord of the Rings or The Hobbit. Tolkien started his writing with creating languages and creating the legends at the heart of the Silmarillion. So much of what he is famous for is only just the final part of whole landscape of mythology.
For its amazing scope this is undeniably a 5 star work. However for readability it does not reach those heights so I have opted for giving it four stars. Two things make reading this book easier, having access to a Tolkien atlas. There are several available but I found Karen Wynn Fonstad's The Atlas of Tolkien's Middle-Earth, very useful. Also helpful is access to a Tolkien companion of names. There is an index of names at the back of the Silmarillion but jumping back and forth to it on a Kindle is pretty hard. My old hardback copy came in handy after all.
If there was no Silmarillion then there would no other stories of Middle-earth, so it deserves to be held in highest regard. But don't start your adventure into Tolkien's writings with it. Start with the Hobbit, LOTR and then work your way into the Silmarillion, when you do, you'll be glad... eventually.