Once the adhesive was done drying (48 hours) I have nothing left to do but show off the final product. It is certainly still low grade, but a vast improvement that can now be handled without risk of further damage.

The book was originally a grade condition of POOR / INCOMPLETE (0.5) but now is complete and easily looks like it would fall in the GOOD condition range (1.8 - 2.5). As a final test I am going to submit the book to CGC and see how they grade & label the work done on the book. Note that I did not try to hide any of the conservation work done on the book, this was all about bettering the structural integrity of it - as such you can see the tear seals to the inside front cover. The spine hinges are only visible if you fold open the covers fully, but even then they are easy to miss if you are flipping through the book. 

 

The main obvious tell of there being repair work (other than the tear seals on the inside front cover) is the spine itself, as since the donor back cover came from a different Canadian annual I had to cut away that comics title from it (but I opted to leave the word ANNUAL on it). When compared side by side to an original Amazing Spider-Man Annual #1 you would notice that the world 'Annual' should be slightly lower down - aligned with Mysterio's arm rather than above it. A minor difference, but one that I feel works still for such a low grade book as leaving the donor spine mostly intact maximizes the strength of the repair (yes, I could have cut away the word annual and removed the entire middle of the spine wrap to make it seem like it originally was the correct spine, but I'm not trying to hide anything at this point and feel this looks better). This will most certainly result in the book being flagged by CGC as 'Back cover married'.

  

I'm pleased with how the repairs turned out, specifically the strength of the mending (I can hold the book up by a cover and let it dangle without anything giving out), especially considering that this was my first attempt at such a big repair on an actual key book - up until this point most books were only a few dollars at most in value. I am looking forward to seeing how it grades.