Here are some of the puranas and other books in condensed/story format:
Srimad Bhagavatam Condensed
Stories from Puranas
Sri Brahma Vaivarta Purana
Sri Narada Purana
Sri Padma Purana
Sri Skanda Purana
Sri Shiva Purana
Also there are quite a number of translations available for various puranas in English, some are:
Śrīmad-Bhāgavatam (Bhāgavata Purāṇa) ...
And once the normal life was established, they left the earth
In Vedas and other scriptures it is mentioned that once upon a time gods and humans used to live together on earth. But, then the gods left and settled in the heavens. So, this particular statement of yours is true as per scriptures:
In ancient times gods and men used to live ...
The question is
What did humans do that Brahma took away their divinity?
I do not know the source of the story, but I am sure that it is narrated to convey a message in an esoteric sense.
Rig Veda VII.76.4 says
त इद्दे॒वानां॑ सध॒माद॑ आसन्नृ॒तावा॑नः क॒वय॑: पू॒र्व्यास॑: । गू॒ळ्हं
ज्योति॑: पि॒तरो॒ अन्व॑विन्दन्त्स॒त्यम॑न्त्रा अजनयन्नु॒षास॑म् ॥४॥
Those were ...