I would personally use a Dictionary(Of String, String) and not use LINQ at all for this situation:
Code:
Dim bookAbbrList = New Dictionary(Of String, String)() From {
    { "gen", "Genesis" },
    { "exo", "Exodus" },
    { "lev", "Leviticus" },
    { "num", "Numbers" },
    { "deu", "Deuteronomy" },
    { "jos", "Joshua" }
}

Console.Write("Book Abbreviation: ")
Dim abbreviation = Console.ReadLine()
If (bookAbbrList.ContainsKey(abbreviation)) Then
    Dim fullName = bookAbbrList(abbreviation)
    Console.WriteLine(fullName)
End If
Example: https://dotnetfiddle.net/UaqKoj