Warm greetings @vanna!
You are in the right place when it comes to finding new witchy books- there are many witchy readers in the forum and books are a hot topic! 
I recommend taking a peek at the Book Reviews from past session of Book Club, as books are shared and full reviews are given about each:
- Witchy Book Reviews! Spells8 Book Club Reviews Masterlist - Sessions I ~ XV
- Book Club Session XVI: Readers’ Reviews
- Book Club Session XVII: Readers’ Reviews
- Book Club Session XVIII: Readers’ Reviews
- Book Club Session XIX: Readers’ Reviews
- Book Club Session XX: Readers’ Reviews
- Book Club Session XXI: Readers’ Reviews
You can also check out:
- This List of Recommended Books for Wiccans
- The Recommendations Category of the Forum
- The “Books” tag in the Forum
Is there a particular topic you are looking for (i.e Green magick, Kitchen witchery, crystals, tarot, etc)? If so, say the word and I’m sure your coven members will be able to recommend titles by name for you! 
Congrats to you for looking to build your altar- I’m sure you’ll find wonderful ways to decorate it and make it your own! 
A good place to get an overview of what you might add to your sacred space is in the witch tools guide:
People kindly share some pretty amazing pictures of their altars and sacred spaces, so if you’re looking for inspiration I recommend browsing through the Altars Tag here in the forum- there is lots of explore!
I hope you’re able to find some wonderful witchy books and can build up your altar into a beautiful space that brings you joy- good luck and blessed be, Vanna! 