A couple of options:

1. Searchable Text PDF: You can use ImageMagick to convert your source TIFF image files (if you have scanned your pages into TIFF format) into Adobe PDF format. If you have Adobe Acrobat, you can run OCR on it to convert it to a "Searchable" text PDF (aka "text under image" PDF).

     There are variations of this workflow with other tools, but this is the basic idea.

     Tip: Ensure that your TIFF image files are uniformly sized.

2. EPUB Ebook Format EPUB is a ebook standard and at its basic level it is a collection of a (a) metadata file (in XML format), (b) HTML files for each unit of content (such as Chapter/Section/Unit etc., depending on how the book is organized) (c) Image files that are referenced in the HTML files (d) CSS file for styling your HTML.

     There are a number of options for advanced use, but you can avoid almost all of them if you approach it as a basic collection of XML + HTML + CSS files.

     The EPUB itself just uses a folder structure to organize the files (similar to a static website) and the format is a ZIP archive file named with the file extension '.epub'.

     Most of the work in creating the EPUB would be in structuring the HTML/CSS files and creating the XML file.

     Tip: There are many companies/freelancers in India whom you can find on sites like fiverr etc., who can do this as a project for you at a reasonable cost, if you would rather outsource this to an expert instead of doing it yourself.

3. Print-on-Demand If you are interested in creating a print run, that is also possible. A typical workflow would be to (a) scan the pages at high resolution (600 dpi) (b) perform image processing to deskew the images and remove noise and perform quality control (c) batch-align the front and back of the image pages (d) save the page images to TIFF (e) convert TIFF to multipage Adobe PDF.

     You can use this PDF with Print-on-Demand publishers to create a physical copy of the book.

    Note: This requires a cutting/unbinding of the original (you can re-bind the original after the process, if you want to keep the original).

4. Typesetting In this method, you have a typesetter re-typeset the entire book (in Indesign/QuarkXpress/LaTeX etc.,). This is a much more involved process, but offers you flexibility in terms of how you want to layout the content, perform some editorial changes etc.,

    Again, there are companies you can engage to do this for you and manage this  as an outsourced project.