Ask HN: How to get traction for an HN-like social news site?

Do what the Reddit guys did, create different accounts and post stuff under those account names to simulate the appearance of a growing community. Classic chicken or egg problem.

any relevant sources?

Fill in content, make regular updates with content - and if the content is well curated, people linked to the discussion threads will stay.

So you'll have to do the work of many at first.

What's the niche? Or is that sekrit still? If you're looking for a niche, btw, there might be one for eBooks/books.

Subscribe it to relevant RSS feeds.