Chess notation

It means guess.  That's all the authors are doing anyway. What good would it do you if they just gave you all the answers? You wouldn't learn anything.  The purpose is to make you think. That's what "?" does. It makes you think

But seriously, Google is your friend. Unless mega corporations scare you:

http://en.wikipedia.org/wiki/Chess_annotation_symbols

?? (Blunder)

The double question mark "??" indicates a blunder, a very bad mistake. Typical moves which receive double question marks are those that overlook that the queen is under attack or overlook a checkmate. A "??"-worthy move often moves a player from a winning position to a draw or loss, a drawn position into a losing one, or an eventual losing position into an immediate loss. They occur at all levels of play to all human competitors, but only the most basic computer programs commit such obvious mistakes.

? (Mistake)

A single question mark "?" after a move indicates that the annotator thinks that the move is a poor one that should not be played. These often lead to loss of tempo or material. The nature of the mistake may be more strategic than tactical; in some cases, the move receiving a question mark may be one that is difficult to find a refutation for. A move that overlooks a forthcoming brilliant combination from the opponent would rarely receive more than one question mark, for example.

Whether a single or double question mark is used often depends on the player's strength. For instance, if a beginner makes a serious strategic error (for instance, accepting gratuitous pawn weaknesses or exchanging into a lost endgame) or overlooks a tactical sequence, this might be explained by the beginner's lack of skill, and be given only one question mark. If a master were to make the same move, some annotators might use the double question mark to indicate that one would never expect a player of the master's strength to make such a weak move.

?! (Dubious move)

This symbol is similar to the "!?" (below) but usually indicates that the annotator believes the move to be objectively bad, albeit hard to refute. The "?!" is also often used instead of a "?" to indicate that the move is not all bad. A sacrifice leading to a dangerous attack which the opponent should be able to defend against if he plays well may receive a "?!". Alternatively, this may denote a move that is truly bad, but sets up an attractive trap.

!? (Interesting move)

The "!?" is one of the more controversial symbols. Different books have slightly varying definitions. Among the definitions are "interesting, but perhaps not the best move", "move deserving attention", "enterprising move" and "risky move". Usually it indicates that the move leads to exciting or wild play and that the move is probably good. It is also often used when a player sets a cunning trap in a lost position. Typical moves receiving a "!?" are those involving speculative sacrifices or dangerous attacks which might turn out to be strategically deficient.

Andrew Soltis jokingly called "!?" the symbol of the lazy annotator who finds a move interesting but cannot be bothered to work out whether it is good or bad.

! (Good move)

While question marks indicate bad moves, exclamation points ("!") indicate good moves—especially ones which are surprising or involve particular skill. Hence annotators are usually somewhat conservative with the use of this symbol; for example, they would not annotate a game thus: 1.e4! c5! 2.Nf3! d6! 3.d4! cxd4! 4.Nxd4! Nf6! 5.Nc3! Although these may be good moves, the players have demonstrated little skill by simply following well-known opening theory in a main line Sicilian Defence.

Once the players start making good choices when faced with difficult decisions, however, a few moves may receive exclamation points from annotators. Typical moves receiving exclamation points are strong opening novelties, well-timed breakthroughs, sound sacrifices, and moves that avoid falling into traps.

‼ (Brilliant move)

The double exclamation point ("‼") is used to praise a move which the annotator thinks really shows the player's skill. Such moves are usually hard to find. These may include sound sacrifices of large amounts of material and moves that at first glance seem like po

Yet, despite that long, detailed description, Knightly News' answer is just plain WRONG.

In that book, the question mark means that the book is asking you the question of what move should be made. It has nothing to do with indicating blunders, as is common when annotating games.

The reason some of them say 1. ? and others say 1... ? is that it's asking you for the first move from this position, either for white or for black. 1. ? means it's white's move. When it says 1... ?, the three dots represent white's last move, and the question mark is to ask you what black's move should be.

@Fromper Thank you so much! I did google around before this and did find the blunder answer, however in context it was clear that it meant something else. I've been playing chess for a while now, but have recently started putting in a lot of effort. 

Thank you for your help :D

Thank you for helping!!!!!!!!