Write queries, not SQL strings.

function SearchBooks(const Title, Author: string; PublishedOnly: Boolean;
  Page, PageSize: Integer): IQuery;
begin
  Result := TQuery.Create('Books as b')
    .Join('Authors as a', 'a.Id', 'b.AuthorId')
    .Select(['b.Id', 'b.Title', 'a.Name as AuthorName'])
    .When(Title <> '',
      function(Q: IQuery): IQuery
      begin
        Result := Q.WhereContains('b.Title', Title);
      end)
    .When(Author <> '',
      function(Q: IQuery): IQuery
      begin
        Result := Q.WhereContains('a.Name', Author);
      end)
    .When(PublishedOnly,
      function(Q: IQuery): IQuery
      begin
        Result := Q.WhereTrue('b.IsPublished');
      end)
    .OrderBy('b.Title').OrderBy('b.Id')
    .ForPage(Page, PageSize);
end;

SELECT [b].[Id], [b].[Title], [a].[Name] AS [AuthorName]
FROM [Books] AS [b]
INNER JOIN [Authors] AS [a] ON [a].[Id] = [b].[AuthorId]
WHERE [b].[Title] like @p0 AND [a].[Name] like @p1
  AND [b].[IsPublished] = cast(1 as bit)
ORDER BY [b].[Title], [b].[Id]
OFFSET @p2 ROWS FETCH NEXT @p3 ROWS ONLY