For those who have enjoyed reading Ven. P.A. Payutto’s Buddhadhamma, I can recommend Ven. Ñāṇananda’s Nibbāna Sermons. While Buddhadhamma covers a wide scope, I found the depth of explanations in the Nibbāna Sermons very helpful.
Ebook formats of Ven. Ñāṇananda’s book are now available to download:
Nibbāna Sermons in ebook formats by Bhikkhu Kaṭukurunde Ñāṇananda