Plus or Minus is a puzzle to help children master the  
skills of addition and subtraction.  Numbers are
arranged in a 5 x 5 grid.  The columns add up to
the answers at the bottom, and the rows add up to
the answers on the right.  The bottom row, the
right-hand column, and the diagonal all add up to the
answer in the bottom right-hand corner, which is left
blank.  Children must place a plus or a minus sign in
front of each number to make sure everything adds up
correctly.  There are three books of sixty puzzles each.

Price: $5.95.
Private I is a board game in a book.  First, it's a game
of imagination.  Children assume secret identities and
then guess who everyone is.  They love it because it
unleashes their ingenuity and challenges their
detective skills at the same time.

Second, it's a game of arithmetic.  Because three
10-sided dice are used to move around the board,
all rolls are strategic.  The numbers on each die can
be either positive or negative, so each roll produces
eight possible moves, four forwards and four
backwards.   The children therefore get to choose
which of the questions on the board they will ask.  
Sample questions are "Does it have an A?" "Is it
soft like babies?" and "Is it a machine?"    

The game is designed to be fun, but it also helps
tremendously with children's addition and subtraction

Price: $9.95.
Both the puzzles and the game
exist as Kindle ebooks, but neither
works well in that format
Math Books and Games