There are plenty of books on the subject these days.

Of the ones I've read, I'd say that probably the most comprehensive book on the Provisional IRA's campaign from 1969 onwards is currently Ed Moloney's 'Secret History of the IRA' which goes into the internal struggles of the Provisional IRA in some depth, particularly focusing on the role of Gerry Adams in changing the IRA's strategy and leading it to the peace process.

If you want to know more about the IRA prior to 1969, I'm under the impression that Tim Pat Coogan's book, The IRA, tends to be one of the more popular ones.

I'm not a historian so I don't know if these books are totally kosher, but I think I've read enough that I can say those are two of the better ones. I'd also think it would be wise to read up more on the conflict in general rather than just concentrating on the IRA itself; the role of the British, and particularly of Northern Irish Loyalists are both very important to understanding how the conflict worked.

The University of Warwick's history department have a bibliography available online from which you can select at your leisure. Of those books, personally I would recommend JJ Lee's Ireland 1912-1985: Politics and Society. Lee is a member of the Royal Irish Academy and his work on Northern Ireland is pretty seminal. /u/Aimhere is also right in recommending Ed Moloney, I can't comment on it personally but it seems to be a go-to text. Tim Pat Coogan is a relatively reliable historian, but his work has been superseded and he does exhibit some bias.

I'd also recommend posting a request to /r/IrishHistory, it's smaller than AskHistorians but you might get lucky.

I got on a kick studying the Irish republican movement a few years back and have some suggestions.

For an excellent overview, I'd recommend Tim Pat Coogan's latest edition of "The IRA." It's one of the most in-depth and readable texts I've found on the subject, and the latest edition covers the Good Friday Accords.

But the IRA is a topic spanning about 100 years, so depending on what era you're interested in, I have a few other suggestions. For a good book on the early IRA and the Anglo-Irish War, I'd go with Peter Hart's "The IRA at War 1916-1923." Another good book about this period is "Bloody Sunday" by James Gleeson. Also, an interesting first-person perspective of this era is "Guerrilla Days in Ireland" by flying column leader Tom Barry, though like with most first-hand partisan accounts take it with a grain of salt.

For the IRA in the Civil War, I'd go with Peter Cottrell's "The Irish Civil War." Unfortunately, I haven't been able to come across any decent books on the IRA from post-Civil War to the Border Campaign, though I'm sure there are some out there.

Now we get to the Troubles, where I think Coogan's "IRA" provides a good overview. But with the Troubles, there are literally hundreds of books that tackle the topic from almost every angle. However, there are three that I've particularly enjoyed. Martin Dillon's "God and the Gun: The Church and Irish Terrorism" offers a lot of first-hand accounts of the motivations of militants on both sides of the conflict. Toby Harnden's "Bandit Country: The IRA and South Armagh" was a great read; it follows the evolution of the IRA's activities in Armagh, and it provides a good insight into how the logistics of the IRA worked (fundraising, recruitment, planning attacks), plus if you're not in the mood for a heavy text this book reads like a novel. Finally, I always liked Laurel Holliday's "Children of the Troubles" - the book doesn't provide much in the way of facts or background, but it is useful in getting a sense of the Troubles' effect on people's everyday lives.

Finally, as a huge Michael Collins fan, I have to recommend Tim Pat Coogan's "Michael Collins," a very readable biography of an amazing man. I would also have a look at "The Path to Freedom," a collection of Collins's essays on Irish history and the independence movement.

EDIT: And here I forgot to address your question about Bobby Sands. There is "One Day in My Life," by Bobby Sands. I admit I haven't read this book, but I figure it's a good place to learn about the man from his own perspective. The Hunger Strikes were never a major point of interest for me, but just thumbing through Coogan's "IRA" I see he has several dozen pages dedicated to the strikes.