Before we go any further, I do want it to be recognized that (a) this is a game I currently play and enjoy. (B) I was given a review copy of the POD version of the rules (thanks again, Simon!). And (C) the primary reason I agreed to do this is to give a little love to OD&D-style gaming, Delving Deeper and the creator of a game that I really, really enjoy.
And so, let us begin our exploration of Delving Deeper by asking "Wtf is Delving Deeper?"
[My questions are in bold, Simon's responses are indented.]
Delving Deeper is, effectively, a '74 white box retroclone (with the addition of thieves as an option). And yet, there are other white box retroclones available or even the "OD&D Single Volume Edition." What inspired the creation of this particular rule set? What was missing from these others that Delving Deeper is uniquely suited to do?
I think I've spoken to most of your question 1 in a recent G+ post here:
The key motivation for DD was originally, I believe, as a legal 0e publishing platform for BHP. While BHP is no longer driving it, this central motivation still remains.
Of the other 0e emulations that were "out there" at the time of DD's inception:
. S&W was seen as covering 3LBBs+Supplements,
. S&W whitebox was seen as covering volumes one and two of the 3LBBs,
. The single volume OD&D PDF was of course illegal so couldn't serve as a legal publishing platform.
. Torch and Sword also appeared around mid 2011, and probably (in my view) ticked most of the boxes very neatly--except that by that time the DD project was already "in flight."
Imagine for a moment that I'm not already positively predisposed toward OD&D gaming. How would you, the person most intimately familiar with the game, convince me to try Delving Deeper?
This question is tricky because it seems to cover some similar ground to question 1, albeit from a different angle. Also it really seems to be two questions, requiring two different answers: (Part A) What do 0e-style games in general (including the original 0e game itself) have to offer? And (Part B) what does DD, a specific 0e-style game, have to offer?
Part A is frequently debated in the gaming community. "Why would anyone bother with those antiquated, 0e-style games?" Here are some thoughts...
* 0e games are accessible. There are few rules a new player needs to know, so even a novice can get involved and have a character in game in a few minutes. And for the experienced guys, all they need for decades of gaming is in three little brown booklets (or if you don't have them, then the one DD booklet will do). It's a whole different level of accessibility compared to, say, the one thousand pages of core rules you get with 5e.
* 0e rules tend to be pretty coarse-grained and don't have lots of modifiers. This makes the mechanics easy to memorise and fast to run. For all the myriad subtleties of "more advanced" rules, they are rarely better simulations and frequently more cumbersome to use.
* 0e games tend to be pitched at just the right level of abstraction to enable a game spanning dungeon, town, and wilderness exploration, and one-on-one duels to battles involving scores (or even hundreds!) of belligerents.
* 0e games are fast paced. Combats run briskly; even major fights that can take hours in other systems can be all over in just minutes. You can get a whole lot done in a typical 0e game session.
* OD&D is deadly (as are 0e games in general) in a way that few other RPGs are. Challenges and rewards are not scaled to be "appropriate." The game can be deadly, but so too the rewards can be tantalizing. Deadly risk plus the possibility of Very Real Reward is a pretty good recipe.
* OD&D is ultimately a rules framework rather than an exhaustively complete and polished system of game rules. It's the toolkit rather than whatever you might build with the toolkit. It can be used "as is," or built on, or adapted into just about anything you want it to be. OD&D is a RPG tinkerer's dream; so much can be done with it so easily!
So what then does DD, specifically, have to offer?
Let me start by saying that the original game itself is still "the real deal". It's only because the original materials are becoming hard to get, and because the various sources aren't "easy" to piece together, and because the IP is being kept under wraps, that the 0e-style retro-games need to exist at all.
Given that scenario, DD is one of a number of 0e-style games "out there." So why choose DD?
Probably most importantly (and in contrast to the original) DD is current and available. It's easy to find and price is no barrier to entry--the reference rules and hypertext editions are free, and even the POD soft copy is dirt cheap. So there's really nothing stopping anyone from checking out what all the 0e "fuss" is about.
That aside DD is, to my knowledge, at least as representative of the original material as is any other 0e game. I would say "more so" but of course I'm biased ;) Even allowing for bias, it's my view that DD stands alone among the 0e-style games in terms of its faithfulness to the language and unique features of the original game. If you haven't played the original game, I'd say DD is a pretty good representation of it.
DD is also a "reasonably" mature product in micro publishing terms. There have now been four versions of the DD Reference Rules with each version being tighter and "better" than the last. Quality-wise (in terms of writing, editing, production, attention to detail) I reckon DD is as good as anything else out there--certainly in the "freeware" space.
So, if you're curious about Original D&D but don't have $200 for a collector's white box set, why wouldn't you check out DD for free?
In our correspondence, Simon commented that these two questions might be too similar to have meaningfully different answers. Of course, then he writes a damn good "this is why you should play Delving Deeper" post. To be fair, the first question was mostly "why write Delving Deeper/how is it different?" and the second one is "why play Delving Deeper?"