For this part of the book discussion, I'll just mention chapter 8 of Exegetical Gems in passing, which deals with the Greek article (see 1 Timothy 3:2). Chapter 9 is about the Granville Sharp rule and that's what will be the focus of this entry.
What is the Granville Sharp rule, and why is it so important? The Granville Sharp rule is important because it impinges on whether Jesus is fully God or not: Merkle thinks Jesus Christ is fully God and he believes the NT contains passages that clearly affirm Christ's deity. One such passage is Titus 2:13; the Granville Sharp rule is connected with this verse as we'll see below. But does the Titus passage transparently demonstrate that the rule is true? To Merkle's credit, he calls the Sharp rule a "pattern," which I've hardly seen writers do.
On pp. 62-64 of his linguistic and exegetical grammar, Richard A. Young likewise has a useful discussion of the Granville Sharp rule. Concerning his much discussed rule/pattern, Sharp stated:
"When the copulative KAI connects two nouns of the same case, if the article hO, or any of its cases, precedes the first of the said nouns or participles, and is not repeated before the second noun or participle, the latter always relates to the same person that is expressed or described by the first noun or participle."
Of course there are possible exceptions to this rule such as plural elements, impersonal nouns and proper names. See Merkle, page 40.
According to the criterion set out, Hebrews 3:1 is an instance of Sharp's rule, but John 7:45 and 1 John 2:22 are not. What about Titus 2:13? The Greek text reads (SBLGNT): προσδεχόμενοι τὴν μακαρίαν ἐλπίδα καὶ ἐπιφάνειαν τῆς δόξης τοῦ μεγάλου θεοῦ καὶ σωτῆρος ἡμῶν Ἰησοῦ Χριστοῦ
Merkle surveys three views of Titus 2:13, then he opts for the third view based on eight reasons. The chapter concludes with a quote from Daniel Wallace and Bill Mounce, who both affirm that Titus 2:13 teaches Jesus Christ is fully divine. However, this verse is highly contentious: even some Trinitarians have argued that Titus 2:13 is not an explicit affirmation of Christ's deity.
I'll just briefly state the reasons why Merkle prefers to construe the genitival Ἰησοῦ Χριστοῦ in apposition to τοῦ μεγάλου θεοῦ καὶ σωτῆρος ἡμῶν, which he calls "the traditional view" (41).
1) The antecedent of a noun in an appositional construction generally directly precedes it.
2) ἐπιφάνειαν in Paul always refers to Jesus' first or second coming, but is never used of God.
3) Paul never calls Jesus "the glory" but does refer to him as Savior elsewhere.
4) Paul links Jesus to the concept "Savior" in Titus 2:14.
5) In view of the ancient Jewish-Hellenistic context, it's natural to link God and Savior together, not separate them.
6) The adjective "great" is better applied to Christ since it's never used of God the Father in the NT.
7) "It is not unprecedented to refer to Jesus as God" (page 42). See 2 Peter 1:1, another so-called GS rule passage.
8) Most grammarians, commentators, and English Bible versions construe Titus 2:13 this way.
For other perspectives, see https://fosterheologicalreflections.blogspot.com/2017/09/henry-alfords-notes-on-2-peter-11-and.html
https://fosterheologicalreflections.blogspot.com/2012/06/jerome-h-neyrey-on-2-peter-11.html
Compare https://fosterheologicalreflections.blogspot.com/2021/04/titus-213-jerome-quinn-remarks.html
https://fosterheologicalreflections.blogspot.com/2012/01/kermit-titrud-on-granville-sharp-rule.html