The Sealed Nectar seems to be the most prominent book on the seerah (perhaps because a translation for it is readily available?)..
Regardless..there are other books of the seerah which are wonderful and thorough in content such as:
1. Zaad Al-Ma'aad by Ibn Katheer
2. Min Mae'een As-seerah by Ash-Shammi
3. Seerat Ibn Hisham
4. Fiqh As-Seerah by Al-Ghazali
5. As-Seerah Annabawiyya by Ibn Katheer
6. Ashamae'el Al-Mohammadiyyah by Al-Tirmidhi
and the more "contemporary" (if I may call them so):
7. Mohammad As if You See Him by Ayidh Al-Qarni
8. This is the beloved Mohammad (saaws) by Abi Bakr Aj-Jaze'eriy
The first six are easily available in Arabic (I don't know if you're an Arabic speaker or not)..the last two..may be available in English..especially the one by Ayidh Al-Qarni..many of his books are translated to English..so perhaps this one is available as well..inshallah it is!..Sh. Al-Qarni is a profound writer and lecturer mashallah!
If I haven't provided much help..then pardon me for wasting your time akhi..but I wanted to put down what I know..of course this list is not a limitation..as it can't be..there are heaps of books on the seerah..but since you asked for the best..I listed the ones described as so by most people
May Allah bless you and guard you..ameen!
