@book{Keefe1997-KEEVAR,
    publisher = {MIT Press},
    author    = {Rosanna Keefe and Peter Smith},
    title     = {Vagueness: A Reader},
    year      = {1997},
}

(Keefe / Smith 1997)

RequirePackage{filecontents}
begin{filecontents}{mybib.bib}
@book{Keefe1997-KEEVAR,
    publisher = {MIT Press},
    author = {Rosanna Keefe and Peter Smith},
    title = {Vagueness: A Reader},
    year = {1997}
}
end{filecontents}

documentclass{article}
usepackage{natbib}
setcitestyle{aysep={}} % no comma between author(s) and year
bibliographystyle{apalike}

begin{document}
citep{Keefe1997-KEEVAR}
bibliography{mybib}
end{document}