How can a monograph focus when  "a defendant is culpable for taking an unjustified risk with the interests of others", but not  "whether risking the interests of others itself should be criminalised or  "justifying risk-taking"? In other words, can you kindly distinguish more clearly 1, 2, 3? They look intertwined to me. I never studied philosophy, please explain like I'm 5.
If you're adjudicating 3 (when a defendant is culpable for taking an unjustified risk with others' interests), then aren't you
"justifying risk-taking" in some circumstances" 
and adjudicating WHEN 2 happens (when risking others' interests should be criminalized)?
"taking an unjustified risk with others' interests" means same as "risking others' interests". To adjudicate when these   happen, you have to "justify risk-taking" in some circumstances.
Findlay Stark. Culpable Carelessness (2017).
It is because of its concern with all things considered wrongdoing that Anglo-American criminal law concentrates on the idea of unjustified risk-taking.11 Importantly, the focus of this book is not on the question of [Boldening 1] whether risking the interests of others itself should be criminalised even where the risked consequence or circumstance does not materialise (in other words, whether simple endangerment should be criminalised)12 or about [Boldening 2] the idea of justifying risk-taking. Separate books could be
written about these topics. More will have to be said about them in this book, but the main focus is on the circumstances in which a [Boldening 3] defendant is culpable for taking an unjustified risk with the interests of others.
The term ‘culpability’ is used loosely in criminal law theory.13 There nevertheless appears to be an acceptance, in much of the theoretical literature on criminal law, that culpability is demonstrated through the defendant’s insufficient concern for the interests of others. The idea of insufficient concern for the interests of others links those who hold vastly different perspectives on other issues. For instance, Alexander, Ferzan and Morse and Tadros adopt different approaches to the wider matter of criminal responsibility: Alexander, Ferzan and Morse think choice is the sole basis of responsibility;14 Tadros explains responsibility in terms of character.15 They also adopt different accounts of the justification of punishment: Alexander, Ferzan and Morse are retributivists;16 Tadros supports (in Criminal Responsibility, where he develops his thoughts on insufficient concern) a communication view of punishment.17 They agree, however, that the element of culpability required for a criminal conviction is a demonstration (through choices or ‘in-character’ behaviour) of insufficient concern for the interests of others.18 Furthermore, focussing on the defendant’s lack of sufficient concern for others is one way of understanding accounts of culpable carelessness in terms of ‘indifference’ towards risk.19 The basic understanding of culpability as insufficient concern for the interests of others will thus be adopted in this book. It is the way in which this lack of concern is demonstrated that is more controversial, and which requires much more explanation.
This is not a cause for concern, however. The ‘objective’ aspects of negligence as failure of belief are not unduly troubling. Absent a strong attachment to ‘subjectivity’ – which would require independent justification of the sort that the Exclusive Thesis needs170 – the presence of some ‘objectivity’ is not fatal to a defensible theory of culpable carelessness. ‘Objectivity’ comes in degrees, and the argument here is that negligence as failure of belief is ‘subjective’ enough to suffice for criminal conviction, in a way that a conduct-based view of negligence is not. Where there is disagreement over the proper social expectations concerning risk-taking and belief formation, importantmoral and political questions are, of course, raised.171 But it is not the aim of this book to remove them from the attribution of criminal responsibility and liability. If anything, ‘objective’
considerations are simply made more transparent by the theory of negligence as failure of belief. This might be a good reason to limit the use of negligence as failure of belief, but that is a point not about culpability but about criminalisation. This point will be returned to later in this chapter.